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STATE OF CALIFORNIA 

DEPARTMENT OF NATURAL RESOURCI<3 

WARREN T. H ANNUM, Director 

DIVISION OF MINES 

Ferry Building, San Francisco 



W. BURLING TUCKER State Mineralogist 

San Francisco] Bulletin 135 [October 1946 



PLACER MINING FOR GOLD 
IN CALIFORNIA 

By 
CHARLES VOLNEY AVERILL 




7 



Contributing Authors 
F. W. Collins P. Malozemoff 

L. Ti. HUELSUONK (1 AI. ROMAXOWIT/, 

Olaf p. Jenkins H. A. Sawin 

H. H. Symons 



«.C.S. tIBIlARV 



LETTER OF TRANSMITTAL 



To His Excellency, 

The IIoxorahle Earl AVarren, 

Governor of tlie State of California 

Sir: I have the honor to transmit here^vitl\ for reprinting-, IJnlletin 
l:}5. Placer Mining for dohl in California, of the Division of Klines. Tliis 
volnnie was orioinally prepared under the direction of former State 
Mineralo<iist. Walter AV. Bradley, and published after his retirement, 
in October l!U(i Avhen W. Burling' Tucker held the same position. Since 
the issue of the book is now exhausted and there is still a continued 
demand for it by industry, a second printinji' is recommended by Olaf P. 
Jenkins, one of its authors, who is now Chief of the Division of Alines and 
State AIineralo«>ist. 

The volume is divided into four sections and an apinMulix : Blaccr 
minin<>' methods. (Jeology of placer deposits, I'rospectinji' and sampling- 
placer deposits. Placer mines by counties, and T.aws affecting placer 
mininu-. Eight authors have contributed to the book: Charles Volney 
Averiil. F. AV. Collins, L. L. Iluelsdonk, Olaf P. Jenkins, I'. Alalozemotf, 
C. AI. Komanowitz, II. A. Sawin. and 11. 1 1. Symons. Assend)ling and 
coordinating- the volume were done by C. A'. Averiil. 
Respectfully submitted, 

AVakrkx T. llAXXTwr. Director 
Department of Xatui'al Uesourccs 
October 13, 1949. 



CONTENTS 



Page 

SECTION I. PLACER MINIXfl METHODS 11 

"^mall-scale methods 13 

^^rafjline (lre<l>riiiK 34 

Dryland dredjres 49 

bucket-line dredKinff, by Charles ^I. Roninnowitz and Herbert A. Sawin 51 

Recker-U<)i)kins single-bucket dredj;e. by II. A. Sawin 61 

JiKffing ajiplied to jiobl dredfrinir, bv I'. Malozenioff 63 

Notes on jijrs for irold dredges, by F. AV. Collins 73 

Treatment of black sand 77 

Drift mininj; — Renernl description 81 

A svnopfic presumption reKardins California's drift mines, by L. L. Huels- 

donk 89 

^^ydraulic mining 93 

Debris dams 144 

SECTION II. GEOLOGY OF PLACER DEPOSITS 147 

New technique applicable to the study of placers, by Olaf P. Jenkins 149 

SECTION III. PROSI'ECTING AND SAMPLING PLACER DEPOSITS— 217 

Sampling - 219 

Geophysical prospectiuf? 227 

SECTION IV. PLACER MINES BY COT^NTIES 229 

Amador 231 

Rutte 233 

Calaveras 235 

El Dorado 255 

Fresno 257 

Humboldt 258 

Imperial 259 

Kern 260 

Los Anfjeles 260 

Madera 261 

Mariposa 261 

Merced 262 

Nevada 263 

Placer 271 

Plumas 277 

Sacramento 278 

San Bernardino 282 

San Joaquin 282 

Shasta 283 

Sierra 285 

Siskiyou 293 

Stanislaus 304 

Trinity -305 

Tuolumne 313 

Yuba 315 

Deep gravels dredged successfully, by Herbert Sawin 317 

APPENDIX. LAWS AFFECTING PLACER MINING 323 

The Caminetti Law 325 

Amendments to the 'Caminetti Act' 331 

Definition of hydraulic minings, 333 

Definition of hydraulic mining from Calif(jrnia Civil Code 333 

Trinity and Klamath River Fish and Game District 334 

Protection of domestic water supplies 335 

Placer mining districts 336 



(5) 



CONTENTS— Continued 



ILLUSTRATIONS 

PaKc 

I'hltr 1. I>l;.i;lilic .In-.l::.- :}4 

-. .M.ip slinw iii;c 'I'fili.iry ;;i;i\cl <li;iim(ls. .\<'\:i(l;i f'ouiity In pockot 

.■'.. Xuiiliciii Sicrni \cv;iil:i ;;c(il<.-ic niMji slmwiii'; Tcrtijiry river ohannHs 

.iikI :\r..ili<.r I.n.Ir -..1.1 Im-]| In pocket 

4. Xnilln'iii (';iliri(iiii:i 111,1)), sliowiiii; rixcrs niiil crfcks wliich prodnrod 

ijold In pocket 

Viiiun- 1. riiiiii(i\c .i,',>I(l n-cnverv iiielliods — i.:in. rocker, nrnistre 14 

•2. C.-M i,;ni :iiid hrA,-.\ 2'2 

■■'.. Huckei- 24 

4. ]{ockr-r p;irts 2.". 

r,. Dip-hox 27 

<:. T-oii- loin 2S 

7. P.odiiisf.n S.-mipliii!; M.-icliiiie .•',() 

5. Denver :\re(li:iiiic:il Hold P;iii, siiijile iiiiif witli trommel ^2 

'.). T>(>nver AFecIiniiiciil (Jold I'mii. dii|ilex unit with h-oinmel ?,P, 

1(1. l)r:i;;liiie dred-e under coiislnictioii in sliop ^S 

11. irimd-wiiicli for drn^'liiie dred^re 30 

12. l*o\ver-\viiicIi for dr:if;1iiie dred-e 40 

1.1. Trr.minel for dr:i;,dine dredge on trnck and trailer 40 

14. ])r:i;:]iiie dredyc .sliowiiif; tronime], riflle-shiices. pnmps, and pump- 
screen 42 

1.-. Cn.s.s .section of dred«e-ritHes 43 

](i. Dragline dredge under constniction in field 44 

17. l)ra«:liiie dred},'e — early staf^e of constrnciion 44 

is. Diajcline dredy:e to accomnmdate .''-cn.yd. excavator 40 

1!). Dryland dred;;e HO 

20. Carrville Cold ('omi>any dredge ."4 

21. Hepairiiifi iiucket-line. Yuha No. 20, showing' latest bucket-design HO 

22. Perry Idler HR 

2."i. P.ecker-IIopkins siii'rle-bucket dredge 61 

24. lincket detail, liecker-IIopkins single-bucket dredge 62 

2.~>. Jig ari-angeni(>iits 70 

20. Jig (esling set 72 

27. Honglier .jigs, four-cell block 74 

28. Flow-sheet for use of .iigs on O-cu. ft. dredge 75 

20. Sand-drag, Siimpter Valley Dredging Company, Sunipter, Oregon — 76 

30. Pieach-sand being worked with dip-box, northern Humboldt County 78 

- 31. Method of spiling in loose ground ." 84 

32. Flume for hvdraulic mine under construction 02 

:!3. Pipe install.-ition, 42- and r>4-inch 100 

34. Cutting with giant 104 

3.". Small giant in operation 104 

:\(>. Rnlde elevator used at Redding Creek mine, Douglas City, Cali- 
fornia , 108 

37. liuble elevjitor in use at Redding Creek mine, Douglas City, Cali- 
fornia 110 

.".S. Hydraulic elevator 111 

■*>0. Handling boulders with derrick 114 

40. Sluice-box at hydraulic mine 116 

41. Forking boulders along sluice at hydraulic mine 116 

42. Stacking coiirse tailing with giant; sluice i.s under grizzly 117 

43. Dredge-type riftb's and wooden block ritHes ,__ 122 

44. Looking down from hillside at sluic<- and uiulercurrents 126 

4.'>. Amalgam retorts, bullion mold. :iu<| crucible 138 

40. Dre.lg.'d strip alon- Vnba Uiver 150 

47. Tertiary Central Hill ehannel. Calaver.is County 151 

45. Table Mountain, Tuolumne County , 154 

40. Kffect of siream-bed irregularities; 'shingling' of boulders 155 

(6) 



CONTENTS— Continued 

ILLUSTRATIONS— Continued 

Page 

no. Kxnmple of prpvolcaiiic topoRmpliy l'^>6 

.11. Miip of i)riiK-ipal pli.vsiop;rnpliic provinces of Cjilifornin liiS 

r.2. Worl< of Vald.M- Dred^inp Compjiiiy. Trinity River 160 

T)."!. Tcrnice.s of Canyon Creek, Trinity County 160 

54. Diagrams showinfj development of i)lacers 162 

5.1. Quartz Hill mine, Siskiyou County 164 

r>6. King Solomon mine. Siskiyou County 164 

.17. Salyer mines. Trinity County 166 

r»S. Cross-section of gold-hearing desert stream 167 

.10. 'Placer mining' beach sands at Santa Cruz 168 

60. ]>iagrams of heach pl.acers 169 

61. 'Cohhle wa.sh' and volcanic ash near Knights Ferry, Tuolumne 

County 170 

62. Diagram of down-dropped fault block 172 

(".',. Sketch of dam made by landslide 172 

64. Sketch map of early Tertiary channel and its delta 176 

6.1. Diagram showing likely positions of gold concentrations in a river_ 176 

(»6. Diagrams of Tertiary gravel deposits 177 

67. Diagrams of erosion and eddies in bends of a river 177 

65. Diagram of effect of increased v<'locity on transporting power of a 

stream 180 

60. A'ertical section of a delta (detail) 182 

70. Ideal cross-section of a delta 182 

71. Diagram of oxbow loojis and an anastomosing stream 102 

72. Diagrams illustrating stre.im i>iracy 106 

7."^. Diagrams of dendriiic and trellis drainage patterns 108 

74. :\rai) of alluvial fans. San .Toaiiuin Valley 198 

"7.1. T'dock diagrams showing tilting of Sierra Nevada 109 

7(). Diagr.-immatic geologic cross-section of Table INIountain, near 

Columbia. Tuolumne County 190 

77. Mosaic of aerial photographs (.f Tal)le :Mountain 202 

78. Index of mosaic of Table :Mountain 203 

70. Surface of Table Mount.iin latite b>va flow 204 

SO. Ideal cross-section of river in Sierra Nevada showing faulting of bed 20,5 

81. Wallace Dredging Company, .3-cu. ft. dredge, operating 8 miles north 

of lone in 1046 230 

82. Pearch mine. Humboldt County 259 

83. P.adger Hill i.roperty of S.in .Tuan Cold Company 267 

84. Western Cold. Inc., Relief Hill mine 268 

8.1. Sampling hydraulic bank 50 feet high, McGeachin Placer Gold 

Mining Company 275 

86. Natomas Ciunpany dredge ^ 279 

87. Thurmnn Gold Dredging Company 284 

88. Depot Hill hydraulic mine 285 

80. I'o\erty Hill Properties dredge under construction 286 

00. Removing overburden ahead of dredging with carryall at Lancha 

Plana, Amador County 286 

01. William Richter & Sons dr.-igline dredge 286 

02. Ruby mine, surface plant 288 

03. Ruby mine, underground slusher hoist 288 

04. Ruby mine, timbering. Slusher scraper at left 280 

05. Gobi nuggets from the Ruby mine 290 

00. Dragline dredge at Scandia mine 295 

07. Dragline dredge at ^foccasin mine 296 

08. Steel hull of dredge of Yreka Gold Dredging Company 302 

00. Yreka Gold Dredging Company, dredge under construction 302 

100. Goldfield Conso1id.it<>d Mines Company, hyxlraulic mine 306 

101. Dredge (.f .Tunction City Mining Comjiany 306 

102. Lincoln Gold Dredging Companv, dr.-igline dredge 309 

103. We.-iver Drediiing C.ini.anv, dr.agline dredge 312 

104. Yuba double st:icker dredges 314 

105. Yuba No. 2(» dredge under construction 316 

106. Yuba No. 20 dredge, operated near Ilammonton, California 320 

(7) 



ABBREVIATIONS 



a-e 


alternating current (electric) 


ARS 


abrasion resisting steel (U. S. Steel Corporation) 


c 


carbon 


cfs. 


cubic feet per second 


cu. ft. 


cubic foot or feet 


cu.yd. 


cubic yard(s) 


d-c 


direct current (electric) 


E. 


east 


ft. 


foot or feet 


gpm. 


gallons per minute 


H. 


Humboldt Meridian 


hp. 


horsepower 


hr. 


hour(s) 


Inf.Circ. 


Information Circular (U. S. Bureau of Mines) 


in. 


inch(es) 


kva. 


kilovolt-amperes 


lb. 


pound (s) 


M. 


1000 


M.D. 


Mount Diablo Meridian 


mg. 


milligram (s) 


min. 


minute (s) 


N. 


north 


no. 


number 


oz. 


ounce (s) 


R. 


range 


rpm. 


revolutions per minute 


S. 


south 


S.B. 


San Bernardino Meridian 


sec. 


section (s) 


sq. 


square 


T. 


township 


vol. 


volume 


W. 


west 



SECTION I 



PLACER MINING METHODS 



SMALL-SCALE METHODS 



Introduction 

The following paragraphs describing small-scale placer mining 
during the depression of the 1930 's are abstracted from a report^ by 
the Federal Works Agency, Work Projects Administration, and from 
the letter of transmittal of that report by Corrington Gill, Assistant 
Commissioner. -^ ^ , 

This report shows that hand placering for gold is a vanishing 
frontier enterprise from which it is now next to impossible to extract 
a living. Soon after the depression set in thousands of unemployed 
with their families attempted small-scale placer mining as a source of 
livelihood. "^ During the early years of the rush to the creeks the number 
of would-be miners failing to find gold was 20 times greater than the 
number of miners who had been successful in recovering an amount 
sufficient for even one sale. Disillusionment was rapid, and by 1933, 
a year in which at least 100,000 men tried their hand at placer mining, 
departures greatly exceeded arrivals at the diggings. By 1937 the 
number seeking gold had dropped to approximately 22,000, of whom a 
fifth recovered no gold at all. Moreover, small-scale placer mining has 
generally offered emi)loyment only for a very short time even to those 
Avho had some success. About half of those who found any gold gave 
up the effort within a month, and three-quarters within two months. 
Because climate and stream conditions frequently limit the work-year, 
and because seasonal jobs in other industries sometimes are available 
at higher wages, even the comparatively small number of full-time 
miners worked only eight months out of the year. 

The average gross earnings for the miners who found gold in Cali- 
fornia, where most of the hand placering is carried on, were $6.02 per 
week for the three years ] 935-37, and weekly income of nearly a third 
of the placer operators did not exceed $3.50. These figures represent 
gross earnings for a full Aveek's work; returns per calendar week are 
lower because of broken working time ; net returns are still smaller 
because of commissions paid to bullion buyers and necessary expenses 
incidental to mining. 

When the low level of weekly earnings and the short periods of 
work are known it is not surprising that yearly returns from gold 
placering by hand methods are found to be pitifully small. Gross aver- 
age annual earnings per miner for California ranged from $44 to $59 
in the years 1935-37. 

The survey did reveal one small group of miners to whom placer- 
ing is important. These are the men to whom placering offers an 
opportunity for work in off seasons and to earn something between jobs. 
When lumber camps are idle, when no harvests are offering work, when 
shops are closed for repairs or' waiting for orders, placering provides 

1 Xewcomb, K., Merrill, C. W., and Kiessling, R. L., Employment and income from 
Rold placering by hand methods : Work Project.s Administration, National Research 
J'roject, Rept No. E-14, 1940. 

( l.-i ) 



14 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 




Fig. 1. Primitive g(.kl recovery methi>as- pan, 
by courtesy of The Argonaut ; rei)rintcd from Calif orni 
Geology, April-July 19.1/,, p. til!.'. 



Jounidl of Mines (inil 



something to do even though the returns are small. In certain limited 
areas, therefore, placering may yield enough to men Avitli irregular jobs 
to be of marked aid to them even though it does not yield enough for 
support in the absence of other sources of income. 

If placering is thus looked upon only as a supplemental source of 
income for residents of the areas with placer deposits, it can be made 
to fill a definite but very minor place in the economy of the few com- 
munities in which gold-bearing gravels are found and to help a few 
hundred men at most. 

The needs of the unemployed in the early 1930 's caused many 
persons to grasp at any possible source of income, no matter liow small 
or temporary it might be. Moreover, perplexed local relief officials, 
who were as yet receiving no aid from Federal sources, welcomed any 
possible source of help for the long lines of unemployed that gathered 
at their offices. 

At that critical time fabulous tales of rich gold strikes came to the 
unemployed and the relief officials. The reports were listened to 
eagerly by many, and the farther from the gold streams they spread, 
the more fantastic they became and the more readily they were believed 
and acted upon. The greater the distance, the greater was the urge to 
get to the streams. Many local relief officials even "staked" families 
to gasoline and food for a one-way trip to the new Eldorados. 

The increase in the price of gold from $20.67 in 1932 to $25. 5G in 
1933 and to $35.00 in 1934 made such stories seem even more plausible 
and helped further to stimulate the migration of men to the creeks, 
despite the unfortunate experiences related by most of those drifting 
back from the gold-bearing areas. Stories of those who succeeded in 
making a living and of the very few who made strikes continued to be 
magnified out of all proportion, both in j^assing from mouth to mouth 
and in the press, and brought new recruits to the streams as late as 1937. 



Sec. I] SMALL-SCALE METHODS 15 

It is obvious to those versed in jrold milliner tliat the facts are 
greatly exajr^erated in these stories. To tlie hard-pressed unemployed, 
llo^vever, these accounts sounded like the answer to their need. How 
could they know that for every one who made a strike in placer mining, 
tens of thousands would find little or nothing, that not more than a 
few score at most could possibly expect to develop a profitable lode mine, 
and that large amounts of capital would be required for most of these 
mines ? The experience of the thousands who are unsuccessful in placer- 
ing does not make n<'ws; the story of the man here and there who is 
lucky does. i\Iost of the accounts were stories of success, stories which 
were news but which were misleading to the unemployed. 

Number of Small-Scale Placer Miners 

Many thousands of unemployed and their families joined in the 
gold rush that followed the spread of such success stories. Creeks that 
later had only one or two placer miners per mile sometimes harbored 
100 men or more per mile searching for precious metal in 1932-33. Of 
course no count was ever made of those who flocked to the gold-bearing 
streams, but 100,000 would seem a conservative estimate for 1932 and 
1933. The number probably did not drop much until after 1933, for 
new men kept coming in considerable numbers until 1934. They came 
from greater and greater distances as the stories spread eastward, and 
they came rapidly enough to replace the disillusioned families which 
were leaving. If there was only one turnover from 1932 through 1933, 
it would mean that 200,000 men tried their hand at placering, and that 
there was one would-be miner for every 10 men who were at least 21 
years of age in California in 1930. 

The 12,422 small-scale miners recorded by the United States Mint 
as selling gold in California in 1937 sold metal valued at only $542,186, 
compared with gc^ld worth $1,033,093 sold by 19,463 miners in 1935. 
It might be pointed out also that the greatest productivity was not 
reached until 1936, after the crowds had left and when those w-ho knew 
the business were able to work unhindered by scores of would-be placer 
miners. 

Summary of Findings 

Small-scale placer mining has certain advantages for the able-bodied 
unemployed. It provides a meager income to a few^ without requiring 
much in the way of training or capital. It enables them to work at 
any time without going through the sometimes hopeless process of find- 
ing an employer. And, in addition, mining has given many who took 
it up seriously a new sense of self-reliance, of independence, and of 
initiative. Such results have had a salutary psychological effect on 
many unemployed during hard times. 

To a few who have mined onl}' internnttently and who have relied 
on the creeks to augment their incomes from other sources rather than 
to provide them with a living, placering has proved particularly helpful. 
It has enabled many men, together with their families, to have some 
occupation between jobs, and it has contributed more to the w^elfare of 
these individuals than the small financial returns might suggest. And 
to a very small proportion of the few who have stuck to the creeks fairly 
steadily, placer mining has proved profitable. 

To some who dislike discipline and authority, placer mining has 
proved preferable to other ways of making a living. There are men wlio 



16 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 



13 



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51.818,604 
113.643.986 
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12,662,718 
"12.247.892 
13.648.386 
13.006.469 
11.356.527 
9.887.233 
10.530,372 
11.133.437 
10.826.645 


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10.752.381 
11.067.815 
11.570.781 
11.572,647 
13,833,679 
12,835.084 
11,013.474 
8.690,174 
8.662,879 
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Sec. I] 



SMALL-SCALE METHODS 



17 



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IK IT,A( i:n MINIS*; roK <:(»M) i.v cat.ifoknia [r.iill. i:^") 

prcrrr tri livr on '_•.") (•••nls ii «liiy wliirli tlicy 1 liciiisclvcs ciini tliroujili 
|)la«-or iiiiiiiii-; niflicr timii In \\(irU for wiitrcs or to Jicccpt jnihlic aid. 
rhicei- iiiiniii<r luis ciiiililnl siicli iiicii 1o live tlicir own lives 1o some 
(l«'<:i'('o at least. 

>\notlier small ^roiip to wlioiii siiiall-seale |)Iai-eri!i<i lias been help- 
ful iiii-liules men with outside iiieonies or j)eiisions. These men would 
have had Mothiii<r to do il' they had lived in the eities, hut they can work 
as hard or as easily as they will on the creeks. Kiiowiujr tliat their 
pensions will enable them to live, they work at their own convenience 
and at their own rate of sjieed on the placer <rravels, addinjr a little to 
their income and takin^r advantajre of the fact that livinp: co.sts are lower 
on the creeks tlian in town. Placer mininji: has enabled many retired 
or pensioned jiersons to enjoy healthful work in moderation, to increase 
their small incomes, and to dream of makin«? a rich strike some day. 

Men who have shown that they can live within their means and 
build up their e(piipment out of an income of a dollai* or two a day can 
sometimes secure backiip^' for larmier placer ]irojects that require more 
capital and will return at least a livin<r wa<ie. p]ach year a few men 
demonstrate unusual ability to placer and to conserve their resources 
and are able to lea.se };ood bars and efiuijiment. Only a very few suc- 
ceed in this way, but they prove that it can be done. 

All the men in these fjroups do not add up to 5 percent of tlie small- 
scale placer miners of the country. For 95 percent of those wiio try to 
dei>end on small-.scale placer mininjr for a Hviu}?, it has turned out to 
be a delusion and a snare, primarily because earniufrs are tragically low. 
The output per man-hour from liand methods of placering on the lean 
bars still available is too low to support life in modest comfort. Less 
than half of the nuMi who try it tiiul enoufrh {rold to hold tliem at the 
streams over a month, and half of tliose who stay over a month do not 
remain over 2 months. Even amon<:: the better full-time miners, half 
appear to net less than $7 per Aveek. The result is that most miners 
follow plaeerinfj only casually in the hope of having a "lucky break" 
or in an effort to earn an income to tide them over between other jobs. 

P^arnings from snudl-scale ]">lacer mining, which are too low to 
support individuals, are far too low to support a well-rounded family 
life. Even the more successful miners can make no provision for med- 
ical attention, good clothing, social life, reserves for emergencies, facili- 
ties for recreation, and other such needs. The small-scale j)lacer miner's 
family lives at a bare subsi.stence level and from day to day. The 
uncertain nature of the work — owing to tiu> fact that the gravels at any 
parti(!ular p(»int may give out at any time and force the family to move 
■ — has the further disadvantage of discouraging provision for suitable 
or i)ermanent dwellings and the making or purchasing of furniture or 
household equipment. This asp(>ct of jdacering also makes it ])articu- 
larly diflicult for children to be educated satisfactorily. 

Children are given very limited educational facilities in the moun- 
tain counties at best. When they are reared in tents and shacks and 
are moved from creek to creek, they have access to poor schools oidy 
and cannot iiojie to receive an education equivalent to that given children 
of more settletl families in the more populous sections. They are handi- 
capped in many other ways. Diets are unbalanced, medical facilities 
hard to secure, and social contacts .scarce. 



See. I 1 SMAT,T,-S('Ai.i', Mi/rnons 1!) 

l''iii;illy, rjiinilics find coiidil ions discourjij^int:' hccansc* llie conniniii- 
ity life is s(» iinsjil isTfictoi-y. Il is (juilc (lill'crcnt. i'l-om that of the 
oi'ijiin.d pionciM's or ovou o!' I'ai'in lainilics. J'ionocrs and i'annors tVol 
that th(\v <)^\■n the hmd and aro (l('V('h)|)in«;- it; tlicy are the jx'oph' who 
count; they aro tlio coiniHiiiiity, and tlicy are able to iiiako a comniunity 
life of their own even with veiy limited physical facilities, liut the 
j^laeer miners are temporary interloi)ei"s. Tliey own no land and are 
not (levelopinji- the area ; they are livin<>' otf, or at best, in the community, 
not as i)art of it, and they do not have the resources with which to 
make a life of their own nor with which to purchase an entree to the 
life of tlie connnunity in which they are living. Famih' and social 
life are very circumscribed. 

Not only was the life of Ihe small-scale placer miner unsatisfac.-tory, 
l)articularly if he had a family with him, but the future probably will 
briiig a declining level. Small-scale placer mining in the United 
States provided fewer than 6, ()()() men with an average recovery above 
$3.50 per week gi-oss for more than 1 month out of 12, and it supplied 
fewer than 'AoO men with that recovery for more than 6 months out of 
12. Unless there is a sharp upward change in the price of gold, it 
probably will provide fewer and fewer men with even this much income 
and for shorter and shorter periods each year. 

The reason for such unsatisfactory incomes may possibly be better 
understood when it is recalled that small-scale placer mining by hand 
methods is an attempt to extract a living from a parsimonious Nature 
by human muscle, with very little aid from tools. The only energy 
provided by other than human exertion is a little free water power and 
power drawn upon by about a third of the full-time miners who utilize 
gasoline engines to pump water. But even these miners, more fortunate 
than the rest, shovel gravel themselves. 

Wherever human muscle, unaided by power equipment works 
against nature, it is an almost universal result that returns are very 
low unless the work requires great skill. This holds true for placer 
mining. If bars are exceedingly rich, as many of them were for a 
time in the late 1840 's and 1850 's, muscle power may extract returns 
for a time comparable with those won by skilled labor in urban centers. 
But when the bars are small, lean, and uncertain in their distribution 
and erratic in their content, as they are in most known auriferous areas 
available to small-scale miners in the United States today, hand labor 
expended on them generally cannot yield earnings comparable with 
wages. 

Mechanized mining can still yield good returns in manj^ areas, even 
on beds with a lower gold content per yard than those being worked by 
hand, because the gold content is certain, the yardage is extensive, and 
the amount handled per man-day with the aid of powder machinery is 
many times the yardage one man can handle unaided by machinery. 
But even when beds are worked by powder, they must be extensive and 
must give a constant yield to be profitable. If they yielded well one 
day, little the next, and nothing the third, as do many bars worked by 
hand, they could not be made to pay no matter how much machinery 
each man could put to work. 

In view of the character of the work and its low returns, the ques- 
tion naturally arises as to why and how men adapt themselves to this 



20 PLACER MI NINO FOB GOLD IN CALIFORNIA [Bull. 135 

jiioiieer type of life and its exceed inf,'ly low earnings. The adaptation 
<»f those \vlio stick to the work is not so difTHcnlt as it nii^rlit appear, for 
the selective process (piickly weeds out those who cannot adjust them- 
selves readily and leaves those to whom the life does not seem strange 
and to whom it may even seem attractive. Men who cannot live on a 
steady diet of canned foods, flapjacks, and beans; who cannot repair 
their own equipment or fix the roof when it leaks; and who dislike soli- 
tude cannot long survive the life at the creeks. 

Phrasing it dilTerently, th.e probability that a miner will adapt 
him.self to i)lacer mining may vary directly with his self-sufficiency. 
If he can live alone, take care of his own needs, work without super- 
vision, and live on a few cents a day, he may become a full-time, small- 
scale placer miner. ^len to whom such a life appeals, or men to whom 
it is not unattractive, can adapt themselves to placer mining, and some 
of them thrive physically on it. But the proportion of workers in 
California, or even in the country, who can meet such qualifieations is 
very small; .so the number who can nuike a success of or even last at 
placer mining is very limited. Men who can fix the roof if it leaks, or 
build it from scratch if necessary, can readily be found; but not many 
men can both fix the roof and stand living alone under it after working 
alone all day. 80 the process of adapting themselves to the creeks is 
primarily- one of selection ; mo.st of those who try it cannot adapt them- 
selves, and leave. 

►Some idea of the difficulties facing a would-be miner entering 
gold-bearing terrain may be realized w^hen it is recalled that many of 
the forty-niners failed on the creeks of California when gold was much 
more plentiful than it is now, and when it is further recalled that in 
the nearly 100 years during which gold has been actively mined, all the 
profitable areas have long since been patented or at least taken up as 
mining claims, or have been purchased for farming or other nonmineral 
purposes. Con.secpiently, a miner who has been successful in locating 
a place that looks promising will ordinarily find that someone else has 
established ownership to it a long time before. 

About half of the miners interviewed who gave infoi-mation on this 
point (102 out of 201 miners) were working without making any effort 
to secure permission; (>;} were working with [permission; 24 owned the 
claims they were working (mostly claims that were .so poor that others 
had passed them by, but that did yield something) ; six i>aid ro;^'alties 
of 10 to 20 percent; and two were supi)osed to pay royalties above fixed 
earnings. The rest worked under various sorts of agreements, sucli 
as acting as caretaker for property in return for the right to mine. 
Owners of rich bars of course will not freely jiermit unrestricted mining, 
but nuniy i)rivate owners of low-grade gravel that will not pay wages 
make no objection to its being mined without royalties provided the 
operation does not become a nuisance. 

The sitimtion is sometimes dilTerent when the men attempt to work 
on the pid)lic domain, for it is the duty of (Jovernment officials to pro- 
tect public i)roperty, ami they have not been enthusiastic over the 
invasion of |)ubli(; lands by miners. The Forest Servic^e, for instance, 
has a very useful policy of keeping a strip of land a (piarter of a mile 
to half a mile wide, on either side of major scenic liij.diways, in it,s 
primitive state. Its oflicials naturally object to the huildiuiior hovels 



Sec. I] SMALL-SCALE METHODS 21 

within this protected area, thoiijjh they sympathize Avith the men and 
aHow tliem to build lialf a mile back from the road. But this means that 
the miners must maintain their own drives to their shacks, which is a 
real hardship in muddy Aveather. The danger of forest fires is ever 
present, and the Forest Service also must be very careful that careless 
miners do not become a fire hazard. Game wardens may object to the 
l^resence of the small-scale placer miners, who sometimes muddy waters 
and hunt or fish without regard to game laws. The muddying of water 
used for irrigation purposes may also create difficulties at times. River 
pollution is another problem where miners work on streams whose Avaters 
are used by towns or cities, and restrictions imposed by sanitary districts 
sometimes add to the miners' difficulties. One of the first adjustments 
the miners must make, consequently, is that of accommodating them- 
selves to property rights which deprive them of the chance to Avork the 
bv?st bars AA-hich already are privately owned, and to laAvs and regula- 
tions Avhich interfere Avith operations on the poorer bars on the public 
domain. 

Those persons Avho insist on trying small-scale placer mining in 
spite of the above Avarnings Avill find methods described by Boericke.- 
Numerous practical suggestions by a man aaIio states that he has per- 
sonally made a living from small-scale placer mining over a period of 
years are contained in a recent book by Douglas.^ Small-scale devices 
described beloAV are suitable for sampling large gravel deposits to deter- 
mine Avhether the gold-content is sufficient to justify Avorking by machin- 
ery on a large scale. Descriptions of the pan, rocker, dip-box, and 
sluice-box are reprinted Avith minor changes and additions from an 
article by Symons.'* 

Pan, Rocker, Dip-Box, and Sluice-Box 

The equipment and operations described herein are among the 
simplest, and have been used in California to recover gold from placers 
since the days of '49. They are used not only for gold, but any hea\'y 
materials may be separated from lighter ones in this Avay. They are 
adaptable for the separation of cassiterite (stream tin), tungsten ore, 
cinnabar, platinum metals, and gem stones. 

Gold-Pan and Batea 

The gold-pan is used in prospecting for gold, in cleaning gold-bear- 
ing concentrates, and in the hand-Avorking of very rich deposits. It 
is a shalloAv pan which varies from 15 inches to 18 inches in diameter at 
the top, and from 2 inches to 2^ inches in depth, the sides haA'ing a 
slope of about 30°. It Aveighs from 2 to 3 pounds. It is made of a 
heaAy-gauge steel Avith the rim turned back over a heaAy Avire to stiffen 
it. Where amalgamating is to be done in the pan, it is either made 
of copper or has a copper bottom. AVhen used by a skilled operator, 
it has a capacity of from half a 3'ard to 1 yard in 10 hours. 

The object of panning is to concentrate the heavier materials by 
Avashing aAvay the lighter. To do this most efficiently, all material 

2Boericke, AA'illiam F., Pro.specting and operating sniaU gold placers, 2d ed., New 
York, John AA'iley & Sons, Inc., 1941. 

'Douglas, Jack, Gold in placer: published by Jack Douglas, Box 21, Dutch Flat, 
California, 1944. 

* Symons, Henry H.. The pan, rocker, dip-box, and sluice-box: California Jour. 
Mines and Geology, vol. 30, pp. 126-135, 1934. 



I'LACKU MlNIXCi roK (iOI.I) IN ('ALII'(ti;NIA 



ir.ull. i:{5 




Reinhitid from Cdli/i 
CcoliKjy, Ai>iil /.'«.{,'. I), iit't 



should be of as even a size as possible. The pan is filled about three- 
quarters full of ^'ravel to be washed, then it is subinerjied in Avater. 
First the larjie p:ravel is picked out by hand, then the clay is broken 
up. after -which the operator raises the i)an to the ed<>e of the water, 
inclininj; it slightly away from him, moving it with a circular motion 
combined with a slight jerk, thus stirring up the mud and light sand 
and allowing it to float oft". 

This is continued until only the heavier materials remain, such as 
the gold, black sand and other minerals having a high specific gravity. 
These concentrates are saved until a large (piantity accumulates, after 
whidi the gold is separated from them. It may be i)icked out by hand, 
amalgamated with q\iicksilver, sometimes in a copper-bottomed pan. 
In some cases where the separation is extremely difficidt and the quality 
and (juantity justifies the concentrates are shipped to a smelter. Pan- 
ning may be best learned by watching an old-timer or experienced oper- 
ator at work, learning certain tricks in the trade from him. A clean 
6- or 8-inch frying j)an makes an excellent prospecting or clean-up pan. 
It is well to burn out an iron pan after having used quicksilver in it, 
and then polish it with a soft rock or piece of brick, otherwise it may 
be impossible to see small colorjj or flakes of gold. 

The batea is cone-shaped and is the equivalent of the pan. It is 
made of wood or sheet metal. It varies from 15 to 24 inches in diameter 
and has an angle from I.IO'^ to l.');')" at the apex. Many persons claim 
that wood will liold fine gold better than metal. The batea is in common 
use in Mexico, Central and South America, and Asia. A shallow wooden 
chopping bowl may be utilized as a substitute for the batea. This woidd 
be u.sed in the same niiiiincr as a pan. 

Rocker 

The rocker is a machine to save gold from auriferous .sands and 
gravels by concentration (sometimes in conjunction with amalgamation). 



See. I] sMAiJ^-scArii: Mr/rnoDR 2:{ 

Rockers vary <rroiitly in size. sliai)e, and <r(MU'ral eonstruction depend- 
ing on ideas of builders in different localities and on their experience. 
Desifjns vary also because of diffei'ent materials beinj; available and 
because of variations in the sizes of tlie ])articles of <ro]d to be recovered. 
Rockers vary in len^^th from 24 to ()() indies or more, in Avidtli from 12 
to 24 inclies, and in height from (i to 24 inclies. Some luive a sinjrle 
apron, and otliei's two ai)rons and sci-eens with lioles as much as half 
an inch in diameter. A <ireat variety of devices to recover the K^ld is 
found : riffles of all kinds, blanket, carpet, rubber mat, cocoa mat, canvas, 
cowhide, burlap, and amal^'amated copper plate. The writer would 
sugrprest as a fairly efficient and easy construction of riffles for a rocker, 
to clamp f-inch metal lath over a double thickness of blanket so that 
it can be easily removed for cleanin<i:. Of all wet placer methods for 
saving ?old, the rocker is one of the most economical on water for the 
amount of material handled. The average rocker when operated by 
two men has a capacity of about '■] to 5 yards in 30 hours, using 100 to 
800 gallons of water. 

Construction. Rockers are built in three distinct parts, consisting 
of a body or sluice box, a screen, and an apron. The floor of the body 
holds the riffles in which the gold is caught. The screen catches the 
coarser materials and is a place where clay can be broken up to free 
it of all small particles of gold. The apron is to carry all material to 
the head of the rocker, and is made of canvas stretched loosely over a 
frame. It has a pocket or low place on which coarse gold and black 
sands can be collected. 

The accompanying drawing (fig. 3) gives a suggestion for a knock- 
down rocker that can be built by any one. The six bolts are removed 
to dismantle the rocker for easy transportation. The material required 
to construct it is given in the following tabulation with dimensions in 
inches : 

A End, one piece 1" x 14", 16" Ion}? 
B Sides, two pieces 1" x 14", 48" long 
C Bottom, one piece, 1" x 14", 44" long 
D jNIiddle spreader, one piece 1" x 0", 16" long 
E End spreader, one piece 1" x 4", ir»" long 
F Rockers, two pieces 2" x 5", 17" long 
H Screen, about 10" square outside dimensions with screen bottom. Four pieces 

of 1" X 4", 15:}" long and one piece of screen 16" square with i" or i" openings 

or sheet metal perforated with similar sized openings. 
K Apron, made of 1" x 2" strips covered loosely with canvas. For cleats and apron, 

etc., 27 feet of 1" x 2" is needed. Six pieces of §" iron rod 19" long threaded 

2" on each end and fitted with nuts and washers. 
L The handle, in the drawing is placed on the screen, although some miners prefer 

it on the body. AVhen on the screen, it helps in lifting the screen from the body. 

If 1- by 14-inch boards cannot be obtained, clear flooring tightly 
fitted will serve, in which case about 12 feet of 1- by 2-inch cleats in 
addition to that above mentioned will be needed. 

A dipper made of a tomato can (no. 2-i) and 30 inches of broom 
handle is also necessary. Through the center of each of the rockers a 
spike is placed to prevent slipping during operation. In constructing 
riffles, it is advisable to build them in such a way that they may be 
easily removed, so that clean-ups can be made more readily. Two planks 
about 2 by 8 by 24 iiiches with a hole in the center to hold the spike 
in the rockers, are also required. These are used as a bed for the rockers 
to work on and to adjust the slope of the bed of the rocker. 



PLACKK MINING FOR OOr.O IN rAI,IKORMA 



f Bui 1.135 



< 




Sec T 



SMALL-SCALE METHODS 



25 




A, 



— >- 



\..... 



1 






2(> rLA( i:i< Mi\iN(^ roit hold in calii-oknia [liull. n") 

Assembly. The jiarts arc cut fo si/c as sliowii on tlic drawinrr, 
fipure 4. The cleats on parts A, B, (', and I) are of 1- by 2-inch material 
and are fastened with nails or preferably screws. The screen (H) is 
)iailed tofjether and the handle (L) is bolted to one side. Corners of 
the screen should be reiufoi-ced with pieces of .sheetnietal because the 
screen is beinjr continually pounded by the fall of rocks when the rocker 
is in use. The apron (K) is a fi-aine nailed to<jrether, and canvas is 
fastened to the bottom, .joints af the corners should be stren{?thened 
with strips of tin or other metal. 

Parts are a.s.sembled as follows: bottom (('), end (A) with cleats 
inside, middle spreader (1)) with cleat toward A, and end spreader (E) 
are placed in position between the two sides (B) as shown in figure 3. 
The six bolts are inserted and the nuts are fastened. Rockers (F) 
should be fastened to bottom (C) with screws. Apron (K) and screen 
(II) are set in i)lace. and the rocker is ready for use. 

If one-quarter-inch lag screws ai'e driven into the bottom of each 
rocker about 5 inches to each side of the sj)ike, and if the head is allowed 
to protrude from the wood, a slight bump will be caused as the machine 
is worked back and forth. This additional vibration will help to con- 
centrate the gold. If these are used, metal strips should be fastened 
to the bed-plates to protect the wood from wearing. 

Opcratiun. AVhen the ground to be worked has been found, the 
miner picks a i^lace near his source of water for his rocker. The fii"st 
thing to do here is to set the bed-plates so that the spikes in the rocker 
fit in the hole in the i)late and so that the iloor has the i)roper slope. 
This slojie is decided according to the ground to be worked. AVhere 
most of the gold is coarse and there is no clay, the head bed-plate should 
be 2 inches to 4 inches higher tlian the tail bed-plate; where most of the 
gold is fine or clay is present or a combiiuition of both, this slope is 
les.sened sometimes to only an inch. It is hard to save very fine gold 
if very muddy water is used, as the operation does not let the fine gold 
settle out but rather fioats it off. 

After the rocker is jilaced in i)osition, the screen box is filled with 
gravel, which is washed off by ])ouring water over this material with 
the dipper. The larger gravel, when clean, is either picked out with a 
fork or by hand and all clay is broken up into a nuid. Next the machine 
is rocked vigorously for several minutes, and water is added continu- 
ously. If all material that will ])ass through the screen has dx)ne so, 
the box is dumped and this operation is repeated until it is thought 
necessary to clean the apron. The apron should be cleaned several times 
a shift, as all coarse gold is caught there. The concentrates are placed 
in a pile for further cleaning. The riffles are cleaned whenever it is 
thought necessary, but not nearly as frequently as the apron, and the 
concentrates are saved for further cleaning. When a blanket is used, 
it should be wa.shed out carefully in a tub of water, as here a good 
percentage of the fine gold is found. All concentrates are cleaned 
further in a ])an. It is important to u.se the right amount of water. 
The use of too nnich water will carry the nuiterial through this machine 
too qjiickly. and with it nnich ^M.ld. When not enough water is used, it 
makes a mud which will not let the fine gold settle. 



SlV. IJ 



8MAI.L-SCAT.E MF.TIIODS 




Fi<J. 3. A din-bcix or shi>rt sluice, with imn screen for riffles. 
J'li'iti) bu Tlios. Whitt : >■( Driiittd froin Calitornia Journal o) 
Mines and Gt ohxni. AprU-.l iihi I'.i.i ',. p. 1 .! ',. 



Dip-Box 

This is a modification of the sUiiee-box and may be used where 
Avater is scarce and there is not enough grade for an ordinary sluice. 
It is portable and may be carried in an automobile. It will permit 
liandling: about as much dirt in a day as a rocker, though the larger 
stones Avill have to be thro-\vn out by hand. 

The dip-box is simply a short sluice with a bottom of 1- by 12-inch 
lumber to which are nailed sides of three-quarter-inch or 1 inch by 6 
inches. The back end piece may also be of 1- by 6-inch stuff and the 
lower end piece 1 or 1\ inches high. To catch the gold, the bottom of 
the box may be covered with burlap, canvas or thin cari)et. Over this, 
beginning 1 foot beloAv the back end of the box, may be 'laid a strip 
of lieavy wire sci-een of c|nartcr-iiich mesh (made from no. 13 or no. 14 
Avire) 1 foot Avide by 3 feet long. r)in-lap and screen may be held in 
place by cleats along the sides of the box. The diji-box may be made 
() to 8 feet long. Those Avho use it often claim that practically all the 
gold will be saved in the first 3 feet. The box is given a steep grade 
by being set on small trestles, the one near the head end being about 



28 



i'LA( i:i{ MiMN(i lOR r.oi.n iv rAT.nouNrA 



rP.nll.1S5 




Kipriiitfd front Cdlifoniia Joiinuil of Mines and 0((ilofjU. Ainil- 
Jiilji in.i'i. II. t.i.;. 



waist liitrh and 6 inelies to a foot lii<ilier than tlie lower one, near dis- 
charj?e end. The dip-box is used by dumpinjr the sand and gravel, a 
small bncketl'ul at a time, into ti\e back end of box, then i)onrin<r water 
from a dipper, bucket or hose onto it until it is washed through the 
box, discharging over the lower end. The gold will lodge mostly in 
the .screen. Riffles nuiy be i)ut in the lower i)art of the box to stop gold 
passing the screen. Water should not be jioured too violently into the 
box. The larger stones must be thrown out by hand, unless the box is 
fitted with a hopper, or a screen. 

Puddling Box 

Where muddy or clayey material is to be sluiced, the first box of 
the string can be made into a "i)uddling box." This can be 3 feet wide 
by 6 feet long, or any convenient dimensions, with 6-inch or 8-inch sides. 
and no riffles. The clayey material can be .shoveled into this box and 
broken up with a hoe or rake before it passes into the main sluice. 
Lumps of clay in a sluice may pick up and carry away the gold particles. 
Long Tom 

A long tom is an inclined trouirh used to concentrate auriferous 
earths and gravels. It has a greater capacity than a rocker, but also 
uses more water in operation, because the water is the carrying agent 
of the finer materials. The long tom is n.snally of crude co'n.struction, 
being built in two sections, the sluice-box, and the riffle-box (fig. fi). 
The slope is generally 1 inch to each foot in length, but this is varied 
as conditions warrant. The sluice-box is usually about 12 feet long 
and about 15 to 24 inches wide at the head or upper end, and 24 to 86 
inches wide at the tail or lower end. and sides are about 8 inches high 
at the tail. A screen or i)iece of ])erforated sheet metal prevents the 
coarse material from going to the riffle-box. and at the head end is a 
flume or iron pipe from which the water is fed. The riffle-box is usually 
shorter than the sluice-box, and .slightly wider than the latter at the 



Sec. I] SMAI>L-S('AM'; MKTIIODS 29 

tail end. It begins just below tlie first oiK'ninji' in tlie screen, some- 
times bas a more gentle slope. Here tbe rifHes ai-e i)lace(l to catcli tlie 
gold. Tbe box is ol'ten lined witb eanvas as in the rocker, and it is 
best to build detachable riffles. The sluice-box should be made of 2-inch 
lumber to Avithstand the abrasion of the gravel. The capacity of a 
long tom is from 4 to 6 yai-ds in a 10-hour day, per man, two to four 
men working. 

Operation. The groinid to be worked is shoveled into the sluice- 
box and waslied by the water coming from the liead end. One of the 
men will work the material in the trough with a fork, taking the coarser 
gravel out when washed clean and keeping the screen from clogging. 
Clean-ups are made when necessary, usually at the end of the day, but 
ex])erience might show that they should be made oftener. 

Sluicing 

►Sluicing is a method of Avorking auriferous gravels in a flume called 
a sluice-box, or in a ditch, and the method is then called ground sluicing. 
The sluice-box is a crude sloping flume or trough, having riffles on the 
bottom to catch the gold. Dimensions var,y greatly and are governed 
b}'' the amount of material to be washed through the sluice. The slope 
varies from 5 to 18 inches in a 12-foot length. The riffles also vary, 
sometimes there are several kinds in a single sluice, some of Avhich are 
quite elaborate and require considerable work in laying. 

In the rocker and long tom, all the coarse materials are removed, 
but in the sluice all is allowed to pass through, or in some cases a grizzly 
is placed at the head of tbe sluice-box to catch the very coarsest of 
material, allowing much heavier gravel to enter than in the other devices 
previously described. This coarse material serves to grind and polish 
tbe gold, thereby cleaning it and making it easier to amalgamate and 
possibly freeing some material mechanicalh^ held. 

In sluicing, much of the manual labor done in the preceding methods 
is eliminated, as the water does all of the carrying of the material. In 
some cases the mining is done hy hydraulicking or a stream of Avater 
is allowed to fall over a bank and in that way wash the material to the 
sluice. Sluicing requires more Avater than the methods previously 
described, the amount depending upon the material to be Avashed, and 
varying from 20 to 80 cubic feet of Avater to move 1 cubic foot of gravel. 
Coarse gravel requires more Avater than fine, but as the gradd is increased 
the amount of Avater required is lessened. The capacity of the sluice 
box is governed by its grade and amount of water available as Avell as 
its dimensions. In ground sluicing a ditch is dug along bed-rock and 
natural irregularities in the bottom furnish pockets Avhich catch the gold. 

Riffles. Riffles are obstacles placed along the bottom of a sluice 
Avhich form pockets to catch gold by concentrating the heaA'ier materials. 
Numerous forms of riffles Avith innumerable modifications have been 
devised. Some of the best knoAvn are described in the folloAving para- 
graphs : 

Common riffles or slat riffles are strips of AA^ood, iron, or steel extend- 
ing across the sluice box. The abrasion is so great on AA'Ooden riffles that 
replacement is required often and therefore other types of riffles are 
preferred in large-scale operations. 

Pole riffles are frequently used. These are 2- to 4-inch peeled poles 
placed either across or lengthAvise of the sluice box. This type is used 



30 



pi,A( i;k minin<: row coi-o ix caf.ifornia [Hull. 135 




Hiitlirisoi) .saiiip 



■Irs), of llodins 



Miniufni till 



with coarse inatcriai and is efticiont in concentrating? both coarse and 
fine fjold. 

Block riffles are made by pavinj; the floor of the sluice-box ^vith 
wood blocks cut across the grain, and four Indies or more hijjh depend- 
ing on the depth and width of the sluice. They are nailed to narrow 
slats on the end that is to re.st on the bottom of the sluice. The slats 
are naile<l to tlie sides of the blocks, so that a space is left between the 
rows of blocks at the top. Spaces between the rows of blocks form the 
riffles. The blocks may be made either .s(piare or round. This method 
is good for both coai'se and fine materials. 

Kock or stone riffles are made by paving the floor of the sluice with 
rock, either stream [x'bbles or flat stones quan-ied for the i^urpose. 
They are held in place by strips of wood nailed across the bottom at 
intervals. This method is good for both fine and coarse matei'ial, and 
extra good for cemented gravel. 

Zig-zag riffl<'s are slats placed part way across the floor of the sluice 
box alternately from the sides.. Tliis type is good for fine material and 
concentrates in a similar way to panning. 

An undercurrent is a wide flat sluice placed beneath the main 
sluice box and is used for the purpose of saving the tine gold. It is 
usually .') to 20 times as wide as the main sluice and fi-om 10 to 50 feet 
long. It receives its feed from a gi'i/./.ly or scr(>en placed in the floor 
of the main sluice-box. from which the fine material drops into a troujrh, 
which distributes the feed eveidy acro.ss the whole width. Undercur- 
rents usually have a greater slope than the main sluice, because the 
shallow stream is retarded more by friction. 



Soo. T] s.MAiJ--srALr. mktiiods 31 

Small-Scale Placer Machines 
A iVw siii}ill-s(jil(> iiiacliiii(>s for rocovory of f^old from placer ^n-avels 
are described below because they are believed to be valuable for sampling 
large dejiosits to determine wlietliei- the gold-content is great enough 
to justify the use of a dragline dredge, bucket-ladder dredge, hydraulic 
equipment or other expensive machinery. The trend in sampling is 
toward the use of such labor-saving machines instead of the rocker and 
other hand-operated devices described above. Additional machines, 
some of them nnicli different in design from tliose mentioned below, 
have been described in the California Journal of Mines and Geology.^ 
Bodinfion Manvfacturing Company, 2401 Baysliore Boulevard, San 
Francisco, California, has made, on special order, machines for sampling 
placer gravels. The following equipment was included: revolving 
screen 30 inches in diameter by oO inches long })erforated with three- 
eighths-inch holes; 2-inch or 2Tj-inch heavy duty pump; and 2|-hp., 
1400 rpm. Novo single-cylinder gasoline engine. The engine was 
arranged to drive the other machines through belts, chains, and sprockets. 
All machines were mounted on a steel frame, and some were mounted 
on rubber tires to make a two-wheel automobile trailer. 

Denver Mechanical Gold Van is made by Denver Equipment Com- 
pany, 1400 Seventeenth Street, Denver, Colorado. This machine has 
-a motion somewhat similar to that used in hand-panning, imparted by 
an eccentric which makes 240 coniplete oscillations per minute. Power 
for both the eccentric and a pump to furnish water is supplied by a 
gasoline engine of :t-hp. Gravel is placed in a hopper 2i feet above 
the base of the machine and passes over an upper screen with water 
from a spray-pipe. The upper screen is a heavy punched plate which 
passes ^-inch material. The hopper is provided with a lip to hold back 
large nuggets. The ^-inch material passing through the coarse screen 
goes to a fine screen below, and fine sizes pass through to three concen- 
trating pans below. The top pan is of copper and is used to amalgamate 
fine gold with quicksilver. Overflow passes to the two lower pans, 
which are provided with rubber mats covered with heavy wire screen 
of 1-inch mesh to act as ritfles. Manufacturers state that the machine 
is very efficient in recovering both coai'se and fine gold. Capacity of 
a single machine is 1^ to 2 cubic jards bank run per hour. The manu- 
facturer supplies small tronnnels to mount over- either one or two of 
the mechanical pans. Capacity of the duplex' pan plus trommel is 
stated to be 4 to 6 yards per hour. 

Denver Trommel-Jig Unit is ma-de by Denver Equipment Company, 
1400-17th Street, Denver, Colorado. A trommel, jig, gasoline engine, 
and pump are provided. The trommel contains a scrubber-section with 
spiral lifting blades to disintegrate clay or cemented gravel. Rated 
capacities of three diff'erent models range from 2 to 6 cubic yards bank 
run per hour. The jigs are 8 by 12 inches or 12 by 18 inches and 
engines are 3 hp. or 4 hp. All machines are mounted on steel frames. 
As a sparate unit, an amalgamation barrel is available for amalgamat- 
ing the gold in the jig-concentrate. 

= Laizure, C. McK., Elementary placer mining in California, special machines and 
processes : California Jour. Mines and Geology, vol. 30, pp. 136-227, 1934. 



:V> 



OK (iOM) IN CAMFORNIA 



Bull. 135 




Sec. I 



S^IALL-SCALE METHODS 



33 




Fig. 9. Denver Mecii 



iinmel. Photo hij 



G-B Portable Placer Machine is furnished by The Mine and Smelter 
Supply Company, Denver, Cohu-ado. It consists of a hopper, combined 
scrubber and revolving screen, and molded rubber riffles, Avhicli are 
vibrated at 200 strokes per minute. Tanks are provided for re-use of 
Avater, but 60 to 75 gallons of water per cubic yard of gravel are dis- 
charged Avith the tailing, and that amount of make-up Avater must be 
provided. Rated capacity on ordinary gravel tliat contains little clay 
and is not cemented is about 2 cubic yards per hour. Power is furnished 
by a lo-hp. gasoline engine, which drives the scrubber-trommel, pump, 
and riffles. 

Further details about all of the above machines are available from 
the manufacturers. 



34 PLACER MIN'INO FOR GOLD IN CALIFORNIA [Bull. 135 

DRAGLINE DREDGING 

The importance of draj^line dmlginff in California is brou«?ht 
out by table 1, which applies to dragline dredging exclusively. It 
shows the increasing importance of production from dragline dredges 
for pre-war years. The sharp decline in 1942 was caused by war condi- 
tions. Not oidy did the War Production Board prohibit gold mining 
except in si)ecial cases, but ])riictically all of the draglines were put on 
war work both as oxcaVators and as cranes. Manufacturers of drag- 
line excavators nnist have time to replace these machines before drag- 
line dreiiging can be resumed on a large scale after the war. The 
method was in an early stage of development in IdXi, but the niachinery 
and niethods were rai)idlv improved, .so that gross production rose to 
a peak of nearly $8,()0(),obo in 1941. 

The name dragline dredge is used in this article to denote a placer 
mining outfit composed of two separate and distinct units. The dig- 
ging is done by a standard make of dragline excavator, which travels 
on the ground by means of caterpillar tracks under its own power. The 
heavy bucket, which picks up from 1 cubic yard to 3 cubic yards of 
gravel at one time, is suspended by a steel cable from a structural-steel 
,;^boom roughly 50 feet in length. Still larger outfits were in use shortly 
before gold mining was shut down by order of the War Production 
Board. At the Mocassin mine in Siskiyou County, a dragline excavator 
of the Monighan type with a 5-ciL yd. bucket Avas in use, and at Uaytou, 
Nevada, one with a 14-cu. yd. bucket. The one at Dayton did not 
operate long enough to give a satisfactory demonstration of the per- 
formance of an outfit of this size. Washing of the gravel is accom- 
plished on the second unit, which is a barge floating iii a pond. For 
washing out the gold, the barge carries a revolving screen and riffle 
tables similar to the units used on the bucket-ladder dredges. The 
dragline excavator digs away at the edge of the pond, which thus 
advances. To cause the barge to follow, a pull on cables anchored on 
the shore is all that is needed. The tailing discharged from a belt- 
conveyor and sand-sluices fills up the pond behind the barge. The 
dragline dredge has been called a "doodle bug'' by many persons, but 
this is not considered an appropriate name, aiul it is not used here. 

The older type of dredge, on which the digging is done by means 
of a bucket-elevator comprising a chain of heavy buckets, each of which 
is connected by a round pin to the next one, will be called here a bucket- 
ladder dredge. The ladder is the heavy structural steel member that 
supports the bucket-chain. This type of dredge is described in a later 
chapter, Bucket-Line Dredging. 

It is not the purpose of this article to indicate that the dragline 
dredge is in any way superior to the bucket-ladder dredge. The drag- 
liiu' dredge has oi)ened up a new field to dredging, namely those deposits 
that are too small to justify the construction of a bucket-ladder dredge. 
If a deposit is large enough and contains enough gold to amortize the 
capital investment in a large bucket-ladder dredge, and return a suit- 
able profit, possibly a dragline dredge should not be considered. How- 
ever, the large sizes of dragline dredges are considered by some opera- 
tors to be at least as good as the smaller bucket-ladder dredges. 

Bucket -ladder dredges have been made jiortable to a certain extent, 
and may be used on more than one deposit, but the dragline has the 



DIVISION OF MINES 



BUI-L. 135. PLATE 




"HEOn^^B? 



n.Ah4 View 



m 



See. I] DRACILINK DREDGING 35 

Tabic 1. (lohl piofhiriion from (Ira</linc drrdiics, 103.1-1!) '/.l * 





Mines 


WashiiiK 


Cubic yards 


Gold recovered 












producing 


plants 


washed 


Fine 


Vahie 


Avei'age 
per cu. yd. 










(iunces 




19.S3 


3 


3 


1 1 ,500 


75- 


SI, 924 


$0,167 


1934 


4 


4 


604,000 


3,466 


121,138 


.201 


um 


24 


23 


3,900,000 


22,191 


770,701 


.199 


\9:u\ 


30 


2(> 


10,010,000 


49,9()8 


l,748,80i 


.175 


1937 


51 


47 


19,304,000 


94,142 


3,294,970 


.170 


1938 


77 


G8 


24,560,000 


118,108 


4.133,780 


.168 


1939 .. 


142 


109 


31,618,000 


172,519 


0,038,165 


.191 


1940 


198 


lOG 


42,747,000 


205,181 


7,181,335 


.168 


1941 


234 


112 


45,579,000 


225,019 


7,875,665 


.173 


1942 


122 


79 


24,52().000 


117,900 


4,126,710 


.168 


1943 


3 


3 


3,180,000 


14,190 


496,860 


.156 



* Extracted from Merrill, C. W., and Oaylord, TI. M., Gold, silver, copper, lead, 
and zinc in California: U. S. Bur. Mines, Minerals Yearbook, Review of 1040, p. 219. 
See also preprints for 1941, 1942, and 1943. 



advantage in tliis regard. The operating cost per cnbic yard is roughly 
the same on the smallest bucket-ladder dredges as it is on the largest 
dragline. 

The dragline dredge has the following disadvantages: 

1. The nsnal depth to Avhich they have worked in California is 
roughly 20 feet. This can be extended somewhat with the largest 
dragline excavators with ver,y long booms such as the one at the 
JNIofcasin mine in Siskiyou County described later in this bulletin. 

2. The}' will not dig gravel that is hard and compact or partly 
cemented as well as a bucket-ladder dredge. 

3. Bedrock must be soft. No dredge is successful where bedrock 
is very hard and irregular, but a bucket-ladder dredge will dig 
harder rock than a dragline. 

Subject to favorable conditions regarding depth, ease of digging, 
and soft bedrock, dragline dredges are successful on deposits too small 
for bucket-ladder dredges for the following reasons : 

1. Less capital is needed to purchase the dragline excavator and 
washing-plant. 

2. The dragline dredges are smaller and float in very shallow ponds 
because the heavy digging-machinery is not on the barge. 

3. The dragline excavator and the tractor with 'bulldozer' blade, 
\vhich is now practically a standard item of equipment, can 
quickly throw up small dams so that the barge can be placed on 
various terraces and in small tributaries higher than the main 
channel. If necessar}-, water for the pond is pumped. 

4. When one small deposit has been worked out, the modern outfit 
with barge of steel-pontoon construction can be quickly moved 
to another deposit. Such a move involving dismantling and 
re-erection has actually been made in a week's time with the 
regular crew. 



3G PLAPKR MINING FOR GOLD IN CALIFORNIA [Bull. 135 

Lopan* and Mapee^ have written articles on dragline dredges. 
Since those articles were written, washing plants have been mnch 
improved, larger nnits have been pnt in service, and cost per cubic 
yard has been much reduced. 

A few details of the geology of the dragline field southwest of Red- 
ding will be given because conditions are nearly ideal for this type of 
dredging. Gravels being dredged (1940) are in the channels of present 
streams and on low terraces adjacent to the present channels. The 
gravel is seldom more than 10 feet in depth, and most of it is loose 
enough so that it is not difficult to dig. 

I^eneath the gravels of the present streams are sediments of Ter- 
tiary and Cretaceous age, all of which form soft bedrock that the drag- 
line buckets can dig. Several inches to a foot of it are usually taken 
up to recover gold lying on bedrock. To the west of the Pacific High- 
way for a distance of 10 to 15 miles, the Tertiary bedrock is a clay-like 
volcanic tuff dipping below horizontal at small angles to the east. 
Gravels of the Pleistocene Red Bluif formation overlie the tuff in large 
areas, and they should not be confused with gravels of present streams. 
Apparently no concentration of gold occurs in these widespread Red 
Hiutf gravels. In the vicinity of (Jas Point, the bedrock changes from 
Tertiary on the east to Cretaceous formations towanl the west. The 
Cretaceous dips east at a steeper angle, roughly 20^. It comprises 
shales, sandstones and conglomerates in general harder than the Tertiary 
tutf, but a layer near the top is decompo.sed and is s(^ft enough for easy 
digging. 

The gold has no doubt been carried over these sedimentary forma- 
tions from an origin in the igneous rocks, schists, and older sediments 
to the north and west. Clear Creek is one of the principal streams and 
it pa.sses through the French Gulch ^ district, well known for its rich 
quartz veins. Erosion of these has unquestionably contributed gold to 
the i)Iacer deposits. In the vicinity of Igo is a deposit of gravel cover- 
ing many acres to depths reaching 100 feet. It is apiiarently an old 
terrace of (;iear Creek, now high above the present stream. Part of it 
has been mined by drifting and hydraulicking. Part of it has not yet 
been mined. Dry Creek and its tributaries, now (1940) being exten- 
sively dredged with draglines, dis.sect the old Clear Creek terrace, and 
gold has been carried out by Dry Creek and over Cretaceous and Ter- 
tiary bedrock. Hence the ]>lacer gold of Dry Creek is derived lal-gely 
from an older placer deposit. 

Some persons have thought of the Cretaceous conglomerates as a 
possible so\n-ce of the gold, and it is possible that some of the beds of 
Cretaceous conglomerate contain gold. However, an examination of 
tlie boulders in the jilacer deposits shows that many are larger than 
those found in the conglomerates, and that they have apparently been 
washed in by streams originating in the i-rneou's rocks and .schists, and 
in the older Bragdon conglomerate (Carboniferous). The bulk of the 
gold must have been washed along with them. Quartz veins in the 
Bragdon conglomerate are gold-bearing at French Gulch. 

' ''"K'M'- r' ^ • l*'-""'-'" "lining In Ciilifornia with power shovels: CaUfornia Jour. 
.MIrif.v and GeoloKV. vol. .32, pp. :{7;i-.TT7, l'.t3(i. 

Ve'Tgi ■ ^ ' ■■ '^ *<"'^'<^'*''***f"l il'iiK-lln.! dredge : Am. Inst. Mln. Eng. Tech. Pub. 757, 

> Averlll r. v.. 0«ild deposits of the RediliriK and Weaverville quadrangle: Cali- 
fornia .lour. Mines and neolocy, vol. 2;t, pp. .1-7.!. map. 1033. 

Hinds. N. K. A . Oeologic formations of the Rc.lding-VVeavorville districts, north- 
ern California: California .lour. Mines and deology. vol. 29, pp. 77-122, map, 1933. 



Sec. I] DRAGLINE DREDGING 37 

Dragline Excavators 

Dragline excavators of such standard makes as Biicyrus-Erie, Lima, 
Link Belt, Koehring, Marion, Northwest, P. & H., and Thew-Lorain 
are in use for dragline dredging. Details of various sizes, speeds and 
horsepower may be obtained from the manufacturers. Thoenen^ has 
tabulated some of these data in Liforination Circular 671)8 of the U. S. 
lUireau of Mines. Fairly higii digging and swinging speeds are desir- 
able for this type of work, and hence fairly high horsepower. Most of 
the draglines in California were equipped with Ij-cu. yd. and 1^-cu. yd. 
buckets, but those of 3 cubic yards capacity more recently put in service 
give a lower operating cost per cubic yard. Some still hirger ones have 
been used but detailed operating costs on them are not available. Pi-ob- 
ably additional outfits in these large si/.es will be developed in post-war 
years. The 1^-cu. yd. draglines have 5U-foot booms, and the ;3-cu. yd. 
draglines have 60-foot booms. Different lengths are obtainable if they 
are needed to fit different conditions. 

Buckets 

Both Page and Esco buckets have been used. The Esco with five 
teeth will dig harder gravel than the Page, but it dumps more slowly. 
A set of teeth is usually dulled each shift, and must be built up by 
welding. 

Power 

The dragline excavator with l^-cu.yd. buckets for which cost-data 
are given below are powered by D-13000 Caterpillar diesel engines rated 
at a maximum of 130 horsepower. The 3-cu.yd. dragline excavator is 
powered with a 200-hp. electric motor. 

Digging Methods 

Two general methods of digging are in use. The common method 
is to move the dragline excavator in the direction of the channel, and 
reach to each side as far as possible Avith the boom. Each cut is twice 
as wide as the horizontal projection of the boom, roughly 60 feet. By 
utilizing the momentum of the swing, the operator can cast the bucket 
a little beyond the end of the boom. The other method is to move the 
dragline excavator across the channe!, tlius placing the caterpillar 
tracks at right angles to the direction of the digging-cable. Wider cuts 
are possible with this method, and its advocates state tliat bedrock is 
cleaned better. This seems rea.sonable, because in the method men- 
tioned first the arc through which the bucket moves causes a strip of 
bedrock to remain uncleaned toward the exti-eme reach of the boom. 
This can be avoided to a certain-extent by overlapping the cuts, but the 
digging is done under muddy water, and accuracy of this overlap is 
difficult to attain. 

Mats 

The dragline excavator can usually ti'avcl on the ground in dry 
weather, but when the ground is nnuldy or very sandy, mats are needed. 
These are made by bolting together timbers, about 8 by 10 inches, in 
sections -i feet wide and somewhat longer than the width of the tread 
of the dragline excavator. The boom is used as a crane to pick these 
up behind the caterpillar tracks and put them down in front. 

* Thoenen, J. R., Sand and gravel fxcavation, Part I: U. S. Bur. Mines Inf. Circ. 
6798, pp. 23-39, 1934. 



38 



PLAPEK MIN'IXn FOR GOLD IN CALIFORNIA 



[Bull. 135 




Fig. 10. Dragline dredge under construction in shop, showing trommel and 
parts of riffle-sluice.s and staclter-ladder. Photo bii ronrtes}/ of Bodinawi Mannjactur- 
iiKi Cdiiiixiiiy : reprinted from CdUfornici Joitruiil of Mines and Geology, April 
ri.ix. p. io>. 



Tractors 
A traetor of tlio cattM-pillar tyjW powered by a diesel engine is now 
praetically a standard item of ecpiipnient in both drajrline dredging 
and bucket-ladder dredging. It is usually equipped with a scraper or 
bulldozer blade in front and often has a winch mounted in back. The 
]»rincij)al use is for clearing the land of brush and trees. These are 
either juished or pulled to one side or piled for burning. Many jobs 
of handling lieavy parts are possible with the tractor, and it is useful in 
building dams for some locations of the dredge-pond. In dragline dredg- 
ing, tlie trartor and bulldozer are ])articularly useful for smoothing the 
way ahead of the dragline excavator, .so that the latter can be moved 
ahead with a minimum of lo.st time. The tractor and Le Tourneau 
carryall have been used in a few i)laces to remove several feet of soil 
overburden containing no gold. 

Washing-Plants 

The washing-]ilant for a di-agline dredge is mounted on a barge, 
and consists of a ho])per into which the gravel is dumped by the drag- 
line, a revolving screen or trommel, and a belt-i;onveyor to stack the 
coarse tailing behind the barge. Laige streams of water are pumped 
from tlie pond into both the hopper and the trommel. The sands that 
pass througli the screen are washed on inclined tables, which are divided 
by partitions into a number of sluices containing riffles to retain the 



Sec. I" 



DRAGLINE DREDGING 




Fig. 11. Hand-winch for dragline dredge. Photo by courtesy of Bodinaon 
Manufacturing Company; reprinted from California Journal of Mines and Geology, 
April 1938, p. 103. 



gold. The washed sand flows into the pond behind the barge. The 
following descriptions of details have been generalized somewhat to 
cover practice in the state, but they are given with the particular plants 
in mind for which cost-data are tabulated below. The all-steel plants 
are made by Bodinson Manufacturing Company, 2401 Bayshore Boule- 
vard, San Francisco. Welded joints are used throughout. Even the 
corrugated iron housing is tack-welded to the steel frame. 

Hulls 

The barge for a 14-cu.yd. outfit is 30 feet by 40 feet anil is made 
of five pontoons, each 8 feet by 30 feet by 42 inches deep. For the 
3-cu.yd. outfit, it is 35 feet by 48 feet by 42 inches deep, and comprises 
six pontoons, each 8 feet by 35 feet. Steel is i\-inch thick, and all 
seams are electric-welded. Well braced frames for pontoons are made 
of 2^- by 2|- by i^-rhch angles. The earlier barges were made of timber 
frames covered with 3-inch planks, but these are now considered obso- 
lete and are not used. 



40 



PLAf'F.R MINING FOR GOLD IN CALIFORNIA [Bllll. 135 




I'':g. 12. I'liuer-wiiuh lor ilranHne dredge. I'holo. riiuilfsij ni liodinsDn MdiuiltKl nriny 
Cii. : II itnntfil III, til CiiUliiriiid JmiiiKil n) .l/iiifs iiiiil Oioloijii, Aiiril lU.iS. ;>. 10). 

1. W^<T 




Fig. 13. Trommel for druKline dredge on truck and trailer. Rcin-intcd Jrom Cali- 
fornia Journal of Mines and Geoloay, April 19S8, p. 105. 



Sec. I] DRAGLINE DREDGING 41 

Winches 

The barge is pulled ahead and swung: to distribute tailing by means 
of cables anchored ashore and attached to winches on the barge. Hand 
winches are used on the smaller outfits and power-winches on the larger 
ones. On a plant serving a 3-cu.yd. electric excavator the winch is 
driven by a 3-hp. electric motor. 

Hopper 

A heavy hopper usually made of half -inch steel plates welded 
together receives the gravel dumped from the dragline bucket. A 
grizzly of 90-pound steel rails spaced at 16-inch centers prevents large 
boulders from entering the trommel. An effort is made to lay aside 
with the dragline any boulders that will not pass through this grizzly. 
On some washing plants the griz'^ly is inclined dowuAvard slightly toward 
the front of the barge, and boulders are dragged back into the pond 
with the bucket. Water is discharged from nozzles into the hopper. 
On the 3-cu.yd. outfit, the hopper is 14 feet by 10 feet and is 13 feet 
II5 inches above the deck. 

Trommels 

Details given here are for the plants on which cost-data are given 
below. Different sizes of holes and different spacing can be used as 
required by the particular deposit- being worked. For the l-|-cu.yd. 
outfits, trommels are 24 feet long by 54 inches in diameter. Two end 
sections of 4 feet eacli are not perforated. Other sections of 4 feet each 
are perforated as follows: first, f-inch holes with 1^ inches of metal 
between ; second, f -inch holes Avith three-quarters of an inch of metal 
between; last two, ^-inch holes and half an inch of metal between. 
They turn at 14 revolutions per minute. On the 3-eu. yd. outfit, the 
trommel is 35 feet long by 5 feet in diameter. End sections of 5 feet 
each are not perforated. The remainder of 25 feet is perforated with 
^-inch holes, but the spacing varies in the 5-foot sections as follows: 
on the first section 1^ inches of metal between holes; second section, 
^-inch ; last three sections, ^-inch. The different spacing of the holes 
is to distribute the fine gravel evenly to the riffle-.sluices or tables below. 
The speed of rotation is 12 rpm. A pipe drilled Avitli f-inch holes extends 
through the trommel, and water is sprayed from it to wash the gravel. 

The intermittent loads dumped into the hopper cause surges of 
gravel through the screen and sluices. To equalize the flow, some trom- 
mels have been equipped with an Archimedean screw of one or more 
turns in the upper blank or scrubber section. This helps to break up 
lumps of clay and to feed the gravel more evenly into the perforated 
sections of the trommel. 

On the older outfits, the metal housing aroinid the lower half of the 
trommel ended a few inches above the riffle sluices, and water and sand 
dropped directly on the riffles. On the Bodinson washing plants, the 
trommel housing is carried several inches below the level of the riffles 
into a narrow, depressed steel box running the full length of the trommel. 
This is provided with baffles or weirs to regulate the flow to the different 
sluices. It serves also as an effective trap to retain coar.se gold. To 
recover this at cleanup time, large pipe-plugs in the bottom are unscrewed. 



42 



i'i-A( i:h minin<; ion (joi.d in cat.ii 'ohnia IHiill.i:!") 




Fio. 14. DraKli 

Itrprxntril j. 



,1 <./ M, 



-:-liii(t s, ininip. atul luimp-srreen. 
./ (!roU)<ni. Ainil I'.i.iH, ]i. 106. 



Riffle-Tables 

On the .'i-LMi.yd. outfit are 10 sluices with riffles on eacli side of tlie 
tronnuel. Tliey are all ;}0 inelies Avide, t^^•elve are 14 feet lon*r, and eijrht 
are 1 1 J feet lonjr. They discharge into a jiair of sluices of the same width 
on each side of the harjie, ruiniin<r len<j:thwise of the bartj:e to discharj^e 
at the stern. The Jower portions of these sluices are i)rovided with riffles 
also. In the upper portions, where the sluices running? crosswise of the 
bar};e disdiai-jre into them, too nnich turbulence exists for riffles to be 
effective. The trommel and all sluices are set at a j-rade of H inches 
to a foot. Some desi<>iiers use 1 \ inches to a foot. On the smaller barp:es 
for IJ-cu.yd. drajrlines, the arranjrement is tlie same, except that dimen- 
sions are reduced locoi-respond with those of the barge. 

Riffles are of tlie llnufrarian dredire-type of wood, 1^ inches deep, 
3-iiicli wide, spaced at 1] inches. They are made up in sections of a 
lenjrth c(|ual to the ^Vi(lth of the sluice, and about a foot alonp: the direc- 
tion of flow. These small sections are easily handled during: the cleanup. 
The top of the wood is beveled off for an ei<:hth to a quarter of an inch, so 
that the toj) is nearly level when the riffle is in the sluice. It is shod on 
top with strai) iron, 1 inch by i-inch, held in place with countersunk 
wood screws. On the Koarinj; Kiver dredge rubber is substituted for 
ir<»n. But the rubber and the iron are wider than the wood beneath, and 
overiaj) tlie wood a little on both edjres. 

Most operators use expanded metal lath of 1-inch mesh over burlap, 
coconut mattinpr or En}.disli corduroy in the upper half of the sluices 
runniiif? cro.s.swise of the barfre, that is just beneath the trommel. The 
metal lath is raised with t()n<;ne-and-frroove floorinpr so that the top is 
even with top of the riffles in the lower part of the sluice. Quicksilver 
is sprinkled on this at the start of each shift, and the metal lath holds 
the quicksilver do.se to the under side of the flow of sand and water, 
where it is more effective in amalgamating the gold than in the deeper 
riffles. 



See. I] DRAGLINE DREDGING 43 





flo^ 




"V'^^ 


Wm 




'i ^yy\ 






^J-^P=^ 




i 


CROSS SECT/ON 


OF R/FFLES 




O/merrs/ons /n inches 





Cross-section of dredRe riffles. Jieprinted jroin CdUfornia Journal of 
Mines and Geology, April 1VJ8, p. IOC. 



Stackers 



For stacking: the coarse tailing behind the barp^e, the 1^-cu.yd. plant 
is ecjnipped with a belt-eonveyor system, 50 feet long between pulleys, 
with a 8()-im'h belt. The stacker for the 3-c'U. yd. plant is 50 feet long 
with a 86-ineh belt. Some of the boats with diesel power have an electric 
generator and motor so that the .stacker can be driven by the upper 
pulley. One plant has the upper pulley driven by a shaft running the 
full length of the stacker. 

Power , •, 

On one of the H-cu.yd. oiitfits for which ccst-data are given below, 
power is furnished by a D-7700 Caterpillar diesel engine rated at 50 hp. 
on continuous sustained loads or 63 hp. maximum ; on the other by a 
D-8800 Caterpillar diesel engine rated at 64 hp. .^nd 80 hp. respectively. 
Electric lights are furnished by 2000-watt Koehler plants. 

Power on the 3-cu.yd. outfit is furnished by the following electric 
motors: 50 hp. on pump, 30 hp. on trommel, 10 hp. on stacker, 3 hp. 
on winch and 5 hp. on auxiliary pump. 

Water 

During the first half of the year, for which cost figures are given 
below, practically all water needed was obtained from the natural flow 
of the streams. During the dry season.' impounded water bought from 
a company which furnishes water primarily for irrigation may cost 
$500 per month total for all three outfits. 

Water for washing the gravel on the barges is pumped from the 
pond on the 1^-cu.yd. outfits with a 7-inch centrifugal pump. The 
3-cu.yd. plant has a 10-inch pump discharging into the hopper and 
trommel ; also a 4-inch auxiliary pump to supply additional water to the 
sluices. The 4-inch pump is used to furnish water for cleaning up 
the riffles. The proportion of water and sand is variable according to the 
character of the ground being mined. The mixture of sand and water 
discharged at the stern of the barge is roughly 10 to 15 percent solids. 



44 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 



^ 




Fig. lU. Diiieliiie iln-dge under constriu-tinn in (iiki. ICr/nintfil jrom Cali/oritia 
Jounidl of Mines and Gcoloyy. April lU.is. p. itn. 




Sec. T] DRAOMNE DREDGINQ 45 

Delays 

The plants are kept in operation 24 hours per day. "Operating? 
hours" listed below include only that time in which the dragline was 
difrprinj; fjravel and deliverin<j: it to the h()pi)er on the barpje. All other 
time is counted as delays. These include time for movinp:, for lubricating^ 
and servicinji" the di'ajiline and other machinery, and for repairs and 
cleanups. 

For a move to a lunv location involvinji.- dismantling of cfjuipment, 
7 days are required for the H-cu.yd. outfit, and 8 days for the 3-cu.yd, 
outfit. The rej^ular crew of rou^ddy 14 men is used in eitlier case. As 
extensive replacements of worn i)arts are usually made at this time, an 
accurate estimate of the cost of siuth a move is not available. Parts and 
cost of installin*; them should be chai'fied to maintenance and not to 
movin<r. In such a move the dra<iline is used as a crane to pick up a 
pontoon or otlier heavy part and load it on a truck and trailer. It is 
interesting- to note that $1 ,()()() should be ample to cover the cost of 
dismantling; and re-erection when the len<:th of the truck-haul is moderate. 

Merrill^ in Peele's Mininp: Engineers' Handbook gives a table of 
actual costs of six such moves ranging from .$1,470 to $1,656. Transpor- 
tatio)i, partly by truck and partly by rail, was the largest item in each 
case, and ranged in cost from $900 to $1 ,200. Distances ranged from 50 
to 300 miles. 

Cleanups 

Cleanups are probably made on the average of about once a week. 
Some operators could no doubt improve their recovery by watching the 
condition of the riffles more closely and cleaning up when the riffles are 
loaded instead of at regular intervals. One operator who uses expanded 
metal lath over burlap near the trommel cleans up the lath after every 
80 hours of running time, and makes 80 to 90 percent of his total recovery 
in this way. The metal lath is taken up, then the concentrate on the 
burlap is hosed off into a tub. To clean it thoroughly, it is finally held 
in a vertical position over the tub and hosed again. When the Hun- 
j?arian riffles are cleaned up, the sections about a foot in length are taken 
up one at a time, and lighter sands are washed overboard with a hose. 
Amalgam and several tubs full of the heavier sands are saved for further 
treatment. This treatment varies with different operators, and ]ouff 
toms, tables of the AVilfley type, and amalgamation-barrels are all in use. 
Amalgam is squeezed and ivtortcd, and the resulting sponge-gold is 
ready for the mint. 

One operator who recovei's platinum makes the final concentration 
by panning, dries the concentrate, and blo-ws away the last of the sand. 
The metal is then treated with idti-ic acid, washed and dried, and sold 
to platiniun-buyers. 

Crpw 

The c-rew employed on the three outfits for which cost-data are given 
below comprises the following : 18 men on barges, 9 on draglines, 3 oilers, 
3 tractor-di'ivers, 3 mechanic-weldei's, 3 extras used as truckdrivers, etc., 



sMerrin, Charles Wliite, Di-agline dredpiiiK, in Peele, Robert (editor), Mining 
engineers' handbook, Vol. I, s»c. m, pp. ijoO-tlOO, New York, John Wiley & Son.s, Inc., 
1941. 



40 



I'LAcr.R MIXINCl FOR flor-O IN' fAT.II'OFiNIA 



[r.uii. in.') 







^^ 






^^ 


1 — 


T^M , k • 


^v 


M^ 


I 






MUB^^^b 


F 


^1 


m- 








■1 


m 






• 



F'lG. IS. DraKline ilr.dK'- to aoonimodat.- IJ-cii. yd. ex.iva tci-. I'luiti, b/i 
lOurtruM of liixUiiaou MdintJtutHriuii f'ompauy ; reprinted from Cdliforiiid .Imn-nul 
of Miu'fH (iiul Geolofni. April lllSK. ;». ll.i. 



uiif clciiiiiii) iiiaii. and owv siiptM-iiilciidt'iit. Tliis crew ol' 41 iiUMi operates 
thcllircc plains for 24 liom-s per day. 

Capital Investment 

The followiii^r fijriires ai'c iiiteiidcd lo iiive a roii<ili idea ol" tlie cost 
of llie pi-iiicipal items of ('(piipnieiit of liij^li (piality and l)oii<ilit new 
about 1 !):{."). 

Jl-iu.yd. .i-vii.ijil. 

'diesel electric 

nnicli xnivalor ,_ $21>,(KM) $;{(),(KM) 

ItiuK.- .iii'l w!ishiii« plant 2(».()0(> :iS,(HM» 

Ul»7 ("iilripijhir tiiKtor, (licsi'j (J.^CM) 

HI»N Ciil.Mi.ili.u- ti-jKti.r, (li.'M-l S,(MM) 

Alliuliiii.-nls fur tractor ( iMiJldo/.r-r, wiiiclK W^m 

Mis<rllaii«'<)iis wcMiiiK, iMc 1,-,(M) 1,7(M> 

$50,(KK) .$71,(HM» 

III addition to tliese main items, tlie followin}; may or may not be needed 
depending.' on the location and other variable conditions: truck, sliop, 
camp, slock of spare jjarts. electric j)o\ver line and transformers, stora«re 
for diesel fuel. A shop of .some kind is usually ])rovide(l. It nuiy con- 
tain a part or all of tiie followinjr : welding- e(piipment. machiiu' tools. 
retort for anuil;ram. macliincry foi- (•leanin<;- sands, and possibly for 
recovery of platinum. 

Operating Costs 

The following fi^rures on operatinjr costs, coverinjr tlie first six 
montiis of 1I>:{7. were furnished by the auditor of an experienced opera- 
tor who had been in the l)usiness for some time. All of the ecpiipment 
was boujrht new for the purpose of dra<rliiie dredjrinjr and liad been in 
operation for an averajre of about a year before January 1, 19;{7, when 
the period covered below starts. Depreciation of $1,000 per month on 



See. I] DRAGLINE DREDGING 47 

each outfit is clmi-'rod by the ojiorator Avitli tlio idea in mind lliat tlie 
machinery runs continuously, as near 24 hours i)er day as jiossible, not 
intermittently like e(|uipnieiit used by a contractor. Tlie fijrures are 
believed to be accurate, but Avith less accuracy in the fijrure for cubic 
yards than in the others. Yarda<:e uas calculated on the basis of an 
actual survey for area, but depths Averc estimated. Emphasis is again 
placed on the fact that this dredginji' -was done under conditions practi- 
cally ideal for a drajrline. Depth of jiravel was less than 20 feet, it \vas 
recent jrravel of present streams, loose and easy to dip-; bedrock was soft, 
and a foot of it was easily du<i- by the dragline ; the outfits Avei-e operated 
for periods of a year and more on tlie same dejiosits, and no time was 
lost in dismantling for moves; freezing of water during winter was so 
slight that it caused no trouble. The only condition not ideal was the 
presence of growing trees and brush on much of the land. Cost of 
removing this is included in the same account as repairs. "Wages were 
$1.00 per hour for dragline operators and $0,625 for other classes of 
labor during the period. 

The lower cost per cubic yard for the 3-cu.yd. electric is due chiefly 
to the fact that a much larger yardage is handled by the same size of 
crew as is used on the smaller outfits. The cost per cubic j-ard for power 
is a fraction of a cent lower on the electric. 

Ih-cu.Jid. Ih-cu.yd. 3-cu.yd. 

diesel die.sel electric 

Gravel bandied, cubic yards 394,050 3.30,000 690,000 

Cost of Operation 

Dragline, payroll ?4.0o9.10 $4,003.38 .$4,269.20 

Fuel oil, lubricating oil, frasoline 1,.-.00.00 1,471.38 57.03 

Maintenance 1.405.58 1.204.15 889.96 

Cable 592.73 777.03 1,394.97 



Direct expense 8,157.41 7,515.94 6,611.16 



Washing-plant, payroll 5,283.11 4,489.94 6,307.50 

Fuel oil. gasoline 1.2.55.00 1,278.68 160.39 

Maintenance 877.22 825.73 949.48 



Direct expense 7,415.-33 6,594.35 



General operation 

Power 3,599.13 

Water 159.00 

Repair, labor and niatoriaI.><, including clear- 
ing of land with tractors 8.282.11 7,6.58.11 8,301.89 

Compensation insurance 586.70 593.26 585.62 



8,868.81 8,251.37 12,645.64 



Office, taxes, general 1,001.00 875.39 948.80 

Depreciation 6.000.00 6,000.00 6,000.00 



Total operating expen.se, 6 months .$3 1,442.. 55 .'?29,237.05 $33,622.97 

Cost per cubic yard 0.08 0.088 0.048 

Operating hours 2,175 2,489 2,686 

No land-costs and no royaltios arc included in these figures. 



48 PLACKR MIXING FOR GOLD IX CALIFORXIA [Bull. 135 

(lardiicr iiiid Allsiiiaii '• <rivo a table of costs at 21 i)lai-cr mines with 
Hoatinjr wasliiM<r plants, but few details of methods of aecountinj>' used 
to arrive at the fijrures are jriven. The ranjre for most of the plants is 
y cents to I'J cents per cubic yard. Depreciation is incliuled in most 
cases, but not royalties. They state that when all costs except royalties 
are included. 12 cents would probably be about avera<re. Royalties 
usually are 10 to lo percent of the i-ccovered ^old. However, some 
operators bou«rht the land and reduced this cost. Most of the draglines 
covered by this table had buckets of 1 1 oi- 1 \ cubic yards capacity. 

"(Iiinlii.T, !•:. II., aii.l Allsniaii. V. T., 1'o\v.t-s1i,.v.1 aii.l iliaKliiK' phu-.-r iniMiiiK: 
V. .S. Uiir. .Mints Inf. ("ire. Toi:!. pp. tU-0,"j, l".t3s. 



DRY-LAND DREDGES 

Durinji: the early lOMO's a number of the so-called 'dry-land' dredges 
Avere built in northern California. Most of them were so poorly designed 
and constructed that they had no chance to succeed, and were used for 
very short periods. Even the best of them were built on timber skids 
to be pulled forward by the power shovel. Gravel accumulated under 
the skids, irregular bedrock interfered, and much time was lost in moving. 
Another common fault Avas tailing-sluices on trestles, Avhich needed 
rebuilding every time a move was made. Lack of head-room often 
resulted in the tailing backing up against the rear encl of the washing 
plant. Most of tliese outfits Avere built of second-hand material includ- 
ing second-hand gasoline engines. Contrast these Avith the latest drag- 
line dredges, w^hich Avere built of ncAv material of excellent quality, and 
Avhich AA'ere poAA-ered by diesel engines or electric motors. Gasoline 
engines may be considered obsolete for such service. Diesel engines 
soon pay for themselves in fuel-savings. 

A fcAv outfits of later design Avere operated Avith some degree of suc- 
cess, such as the one used by Pantle Bros., in the Lincoln district, Placer 
County. The outfit included a movable land plant, not self propelled, 
consisting of a hopper, trommel, centrifugal boAvls and stacker. It Avas 
mounted on a steel frame supported at the rear on caterpillar treads 
5 feet long, and at the front on 8-inch steel AA'heels. The gage AA-as 12 
feet and the distance from front to rear axle AAas 14 feet. The gravel 
AA-as charged to a 3-cu.yd. hopper and Avas hand-fed to a 4 by 10-feet 
trommel. The trommel consisted of tAvo screens, one inside the other. 
The inner trommel Avas perforated Avith ]-inch holes for a length of 8^ 
feet. The outer screen AA-as 6 feet in diameter and AA-as perforated for 
a length of 4 feet Avith 1- by ^-inch slots, and for a length of 2 feet Avith 
1- by ^-inch slots. The undersize from the trommel Avas distributed to 
four 36-inch Ainlay centrifugal gold savers running at 100 rpm. The 
48-foot stacker, AA'ith an 18-inch belt, AA-hich could be SAvung laterally by 
hand or« raised and loAvered Avith block and tackle, Avas provided for dis- 
charge of the coarse tailing. PoAver Avas provided by a 35-hp. electric 
motor,. and a 2-hp. motor on the stacker. The entire outfit Aveighed 15 
to 16 tons. It AA-as fed by a 1-cu. yd. dragline excavator. 

Humphreys Gold Corporation built some very large machines of 
this type at Clear Creek, Colorado, and Virginia City, Montana, and 
operated them successfully. The one at Clear Creek, Colorado, AA-as self- 
propelled by a 90-hp. gasoline engine and AA-as mounted on the chassis of 
a craAvler crane. The one at Virginia City, Montana, AAas a huge machine 
weighing 500 tons. It Avas mounted on tAA'o tractor cha.ssis, and a third 
set of caterpillar treads. It was self-propelled by 2 motors, each driving 
one of the tractor chassis. The gravel Avas dug Avith tAvo 2|-cu.yd. 100-hp. 
electric draglines, and an auxiliary l^-cu.-ycl. poAver shovel AA-as used to 
clean bedrock. 

Costs, excluslA-e of depreciation and royalty, of the outfit at Clear 
Creek, Colorado are giA*en by Gardner and Allsman ^ as $0.25 per cubic 
yard ; at Virginia City, Montana, as $0.] 183 per cubic yard. 

1 Gardner, E. D., and Allsman, P. T., Power-shovel and dragline placer mining: 
U. S. Bur. Mines, Inf. Circ. 7013, p. 65, 1938. 

(49) 



50 



PLACER MTNINO FOR 001,0' IN CALIFORNIA 



[Bull. 135 




...uii,i (roiii (,...,...,...; ./.,.;; iid/ of Miiirs ntul Grologv, 

JUItlKH 1/ I'.l it, I). .(.'». 



The same corporation had one of these larjje outfits in California, 
but (lurinjj their last prold inininfr in California this ^vas idle and they 
were nsinjr the tloatinfj washinp: plants such as are described under the 
headinj; of dragline dredfrinjr in the precedinj: chapter. 

These washing plants that are designed to operate on dry ground 
have not yet been standardized as well as the floatiuf? washinji' plant. 
They are more subject to mechanical trouble and lose more time on 
account of bofrprinpr down, which results in a hijrher cost per cubic yard. 

Another somewhat similar method of handling: placer gravel is haul- 
ing it with trucks to a stationary washing plant, consisting of a hopper, 
trommel, and riffle-sluices for recovering the gold. The oversize from 
the trommel is usually discharged into a bin, from which it must be 
hauled away with trucks. 

Wni. Von der Ilellen had a successful oi)eration of this kind on 
MeConnell Bar on the Klamath River, Siskiyou County, 6 miles west of 
U. S. Highway flJ). The washing plant and trucks handled 1200 cubic 
yards per day, at an estimated cost of $0.:}5 per cubic yard, exclusive of 
depreciation and royalties. Gravel was excavated from a pit 40 feet 
deep below river level by means of a 1^-cu.yd. gasoline shovel of the 
dipper-stick type. The large amount of handling in trucks is chiefly 
responsible for the high cost. 

This method can be used if the gravel is too tight to dig with a 
dragline or if other conditions are unfavorable to the use of a dragline, 
but the co.st is so high that the gold content of the gravel must be much 
higher than that needed for dragline dredging; otherwise the method 
will not pay. 



BUCKET-LINE DREDGING 

By Chahi.ks M. Romanowitz* and Hrfsbkht A. Sawin** 

Successful bucket-line dredgriiifr in California, as known today, is 
an industry of nearly 50 years standing. I)urin<^ that long period, it 
has, on the Avhole, demonstrated soundness and resourcefulness. Prin- 
ciples today are no different from those applying when dredges of 1898 
to 1906 were being designed and built. Placer gravel containing gold, 
platinum, or other mineral products, recoverable by dredging, must (1) 
be dug, (2) be screened, (3) be washed and the metal saved, (4) be dis- 
posed of to rock and sand tailings. Thus are set up the primary 
problems; how they have been met is a story of constant improvement 
in materials, methods and operating 'know how.' What once was con- 
sidered impossible often has been accomplished. What may look to be 
insurmountable today, in dredging practice, probably will be done in 
the future. Early dredges weighed a hundred tons or less. Today's 
great dredges weigh as much as 3,750 tons. The digging ladder and 
bucket line on a large dredge might weigh 1000 tons. The investment 
for a dredge alone, without propertv or rovaltv costs, can run from 
$100,000.00 to over $1,000,000.00. 

Successful dredging is not entirely mechanical; it involves good 
judgment by owners and operators. A dredge might be operated profit- 
ably in one area, but if moved to another, without redesigning or rebuild- 
ing to meet new conditions, be a complete failure. Many inexperienced 
investors hesitate to spend a comparatively small amount of money for 
prospecting. One feature of placer dredging not common to many forms 
of mining, is the relative simplicity of proving property value, extent, 
and characteristics. Long experience with drilling and shafting has 
developed methods for logging and mapping a gold placer property 
which make it possible to design a dredge best suited to that property. 
The presence of boulders, cemented gravel, unusually hard bedrock or 
other serious conditions can be discovered before a dredge is ordered. 
Depth of deposit and variations in bedrock elevations dictate the digging 
ladder length which will work to best advantage. These are physical 
characteri.stics to be considered ; there are other obstacles, which must be 
understood, such as local ordinances requiring resoiling or leveling or 
prohibiting dredging under zoning restrictions. Stream pollution laws 
will influence the type of tailings disposal equipment needed. Pond 
water sometimes must be lowered or changed by pumping and plans made 
accordingly. These remarks only briefly touch upon the many problems 
in dredging : the thought behind them to suggest careful consideration 
by anyone planning to dredge placer gravel and full investigation by a 
competent engineer with a background of dredging experience. 

Gold dredging in California first was attempted as farly as Septem- 
ber 1850 when the small river boat 'Phenix' was fitted out as a dredge 
and attempts made to mine placer gold from river gravel about 9 miles 
above Marysville in the Yuba River. According to newspaper accounts 
of the day, the dredging principle Avas similar to that now in use. An 
endless chain of scoops brought the mud from the river bottom up to 

* Director of Sales, Yuba Manufacturing Company, San Francisco, California. 
** Sales Engineer, Yuba Manufacturing Company, San Francisco, California. 

(51) 



r,2 I'LACKK MININ<I TOK COI.D IN" fALIFORNIA [Bull.l:!-") 

a rofkcr-waslicr wliidi was pi-oiM-llt'd In tlic same power (.peratiii? the 
scoops. Screens separated the fine material fr(mi the coarse and the 
•Pheiiix' was e(piii>ped with a Tiojiardus Patent Anial«raniator' wliicli 
caiifrlit t'recjr(»ld by the iiseof (inicksilver. 

.1. Wesh'v .Jones, in an article entitled ./o/u.s' I'd iitoscojjc of Cali- 
fornin.^ described the ' I'henix 'as follows: 

"The 'IMu'ni.v' di-cd^in;: machine is seen in the Vnl)a River, a cnm- 
hr<»ns arran«:ement. by which it was desij-iu'd to dra^' nj) sand from the 
bed (»f the river, and obtain jiold in lar«re (piantities. Tt was soon found, 
however, that this machine dredf^ed more money from tiie i)ockets of the 
owners than it did ^'old from the bed of the Vnba. and this kind of 
di-edjrin^' was very sooji aban(h)ne(l. " 

Today, technically minded travelers in the dred<iinjr areas of Cali- 
foi-nia learn that a modern dredfie is a marvel of meclianical efficiency, 
and while according; to ]\Ir. .Jones, it was a method of minin*r "soon 
aban(h)ned." he, of cnni'se, had no way of visualizin<r 20th Century 
(lre(l<.'in<r which be;ian in the Oi-oville area in l.'^DB and lias continued 
snccessfnily thronjili the yeai-s to become a ]n-inci]ial soni'ce of ("alifor- 
nia's<rold pi-odnction. 

Today, two mannnoth dredjies in California excavate jrravel 112 feet 
and 124 feet respectively below water level ajrainst banks 50 feet or more 
liifrh. In other words. «jrold-bearinjr pravels 180 feet below ground level, 
laid down centui'ies, jierhaps ajzes, aj^o by ancient rivers, are beinpr 
dred^red and today contribute to the welfai-e of the connnunity. state and 
nation. I)i-ed<res like these represent an investment well over $1,000.- 
000.00 each. Thousands of men are emjdoyed. both directly in operation 
and in maintenance and manufacture. I^i-edjies are <:reat cons\uners of 
cajntal jroods, steel j^rodncts especially. Electric power is a lar<»e item 
of (»pei-ating exiiense which indii-ectly snp))orts many men and their 
families. Lubricatinjr greases and oils are used by the carloads. Rub- 
ber belts, electric motors, cables and sui)plies of all kinds find constant 
use in dredging. Quicksilver, for saving gold in riffles, is used over 
and over again but eventually must be rejilaced and dredges ]irovide a 
constant market for (piieksilver producers.. 

It is rather startling to come across a dredge working in a field. 
Fnmi a distance, it is not always jiossible to see the pond that it digs and 
which moves along with the dredge. Constantly excavating, digesting 
the gravel. sa\ing gold, and slacking tailings astern; these nu>chanical 
'gold-diggers' operate 24 lioui-s a day. «' )i'diiuii-ily, an oi)erating crew 
consists of three or four men ])ei- shift with three shifts per day. A 
dredgemaster is in full charge ami ])lans his work to comj^ly with the 
owner's instructions. Average actual i-unning time is better than '22^ 
liours for three shifts. It is only by steady and constant operation that 
gold dredging can be made to pay. Only l)y handling a tremendous 
yardage and by operating constantly can returns justify dredging. Since 
dredging started in California, the average value of ground dredged is 
less than 12 cents per cubic yard or in other words, about 7J cents per 
ton. The greater portion of California land dredge<l is of no value for 
other purposes except possibly for a few weeks gi-azing in the spring. 
Agriculturally-minded peoi>le raise the cry periodically that good land 
is being destroyed but they overlook the fact that Avhen land is of more 

"Jones. J. We.sley. Jdiu-.s' panto.scope of CaUfornia : a 'lecture' together with 
pencil sketches depleting the journey acro.s.s the plains to California, section third: 
California Hist. Quart., vol. «, p. 2^4, 1927. 



See. I] iu(Ki;t-m\i: DKKiHiixc;— ROMANowri'z and sawin •):] 

value for luiiiiii^;' lliaii i1 is i'oi- a;ji-i(Milhii'(", mining' must, be jziven prefer- 
oiU'O. Tliis is tnu' not only in ^old niiiiiiij:' hut in other branches of tlie 
industry. One faet often ovei-h)oke(l is that, in California, lliere are 
approximately 4.()()(), ()()() acres of so-calh^d arabh^ hind, nntided. and 
])otential dred<:in<i' huid is oid\- a smaM fraction of 1 ])crcent of liiis lar^e 
acreage. l)red<^in^- oi)eratious ret urn to the owners of the hind dredged, 
in royalty payments, far moi-e than the land could eai-n if planted. The 
owner's royalty properly invested will pay dividends 'greater than the 
land Avonhl earn it"crop])ed. 

Dred^in^' lands are found a<l.iaceiit Mo mountain ranges and have 
been formed in i)ast aiies throii.uh t!te action of streams or glacial iee 
(h^positin^- <:ravel bearing- reconcent rated <xo\(\ values. The California 
])hicei-s were foi-med by streams cuttinu:' throuuli beds of ancient sti-eams, 
several of -vvhicli flowed at i-i^ht anjiles to <he i)res<Mit stream courses. 
In this manner, ori«:inal (h'posits of phicei- uold were reconcentrat(Ml and 
deposited in sufficient (|uantities to mak-e placer dred^iu^' ])rofital)l(\ 
Tlie value pei- yard, as stated aboxc. is not hi.iili but occasionally jiroii- 
ei'ties ai-e found where ])lacer ^old deposits raniie from HiO-'-O ppi" cubic 
yard npward. Mncli of the i^old is (piite fine and some jiold lias been 
)-ecovered wliicli would ])ass tlirouizh a screen of ."^OO-mesh size. Closer 
to the footliills, tlie <i-ol(l is moi-e coarse and naturally, as one <iets into tlie 
hills, nng'^'ets are found. 

The principle of dredjiin.u' is (piite simple, (iood California ])i'actice 
is to (li<>' with the maximum depth I'eached Avhile the ladder is at 45" with 
the water level. Di^'<>'in<i- is started at the top of the bank, and as the 
bucket line moves upward, the di-ed^e swinprs to the left and ri<iht, 
pivot in<r about the spud which is at the stern with its ]ioint imbedded in 
rock tailino's. The spud takes the thrust of di<i'^in<i', distributing' the 
load to the fore-and-aft trusses. Siirin<i-mounted spud keepers help in 
absorbi)!^' shocks and distributing- the load evenly. The side swinp.iu<>' 
is accomplished by port and starboard bow lines which are cari-ied from 
the UJider water end of the di^-.i:in^- ladder to shore blocks and back to 
the bow fairleads on the forward deck, thence to the swin<r-^vinch, usually 
mounted inside the deck house on the starboai'd side. As one drum takes 
up the line, say, on the port side, the other ]iays out a slack line to star- 
board. As the swinji' to one side is com]~)leted, the operation is reversed. 

Material, after it is du<r, is elevated iu the bucket line to the main 
h()I)l)er and is cla.ssified in a revolvin<i- screen which discharj^es oversize 
tailing's to a rubber stacker belt. These larpe tailiu<:s are stacked iu a 
pile and form the rock tailinjis which can be seen iu parts of the AVest. 
These rocks ofteu are used for road buildinji' and other jnirposes after 
bein^' crushed and praded in sejiai-ate plants built for the purpose. 

Fines (usually minus i-inch) are dischar<zed through the screen to 
fiold-savinp- tables equi])ped with llun.uarian riffles ^vitli mercury ti-aj) 
riffles usually used in the ratio of about 4:1. P^'ree f>old readily amal- 
jiamates with quicksilver and is cleaned up weekly and retorted ashore. 
There is endless discussion concerning jrold los.ses which occur with 
the discharpre of fine tailinps overboard from tail sluices. On a well- 
constructed dred<;e, mining- clean placer pold which amalgamates freely, 
it is possible that losses are less than the cost of additional equipment 
and labor to prevent them. IIoAvever, in recent years, jijrs of one type 
or another have been in.stalled on several dredfres, used either as a com- 
plete recovery system or in conjunction w'ith tables and riffles, either 



54 



PLACKR MINING FOR OOIJ) IN CALIFORNIA 



[Bull. 135 




Hi 









p<^ 



-•£■« 

C *^ 4; 



L. C 



3 0)™ 
03 



c'c4 S 

2 ^ S 

.- — c 
- II « 



E 5fE 



Sec. I] DUCKET-LINE DREDGING — ROMANOWITZ AND SAWIN 55 

ahead or behind jijrs. .Tips are old in minin'r, bnt new developments give 
them a place in prold dredjrinp-. They have been nsed for tin in the 
Orient, bnt were a l()M<r time in findinjr favor amonjr gold men. Amal- 
jiamators and other mechanical devi-es are needed with the ji*?s and 
extra men are recjnired to operate this department. Ynba Consolidated 
(Joid Fields' dredjres in California. nsin«r riffles for <rold saving for many 
years, are now being e(|Mi|)ped with modern Ynba jigs of new design and 
iiigh efficiency. Long tests indicate that improved recovery will jnstify 
the added investment. 

:\rost California di-edges are electrically operated with power con- 
ducted from conne<-tions on shore througli submarine type cables. 
Transformers on board step down power to usable voltages, usually 440. 
Several dredges in California, notably the newer ones OAvned by Natomas 
Company, convert a-c i)ower to d-c power on board. Bucket lines and 
other units have d-c motors for a wide range of speed. In barren ground 
the buckets dump at speeds as high as 40 per minute ; in hard digging the 
speed can be reduced to a few per minute. The new Natomas dredges 
were designed and built by Natomas C(mipany engineers. Bow swinging 
lines and hoisting lines are synchronized Avith the bucket speeds. The 
company claims many advantages for this type of control. Natomas 
Company also has been 'jig-minded' for many years. Its new dredges 
make use of Pan-American and Bendelari jigs as primary- gold savers and 
riffles for secondary gold saving. 

Easy digging gravel once was almost a general condition for Cali- 
fornia dredges but most of it Avas soon Avorked out. As dredges moved 
aAvay from river and bench gravels and started to Avork on old channels, 
much harder digging became the rule. Dredges must dig into bedrock 
to save rich material lying on it or in crevices. Today's dredges are 
built to cut and dig into hard bedrock or cemented graA'el. One Yuba 
dredge in California. oAvned and operated by Carrville Gold Company 
near Carrville, Trinity Comity, digs at a depth of 50 feet beloAv Avater 
level using 12-cu.ft. buckets. Its poAver and digging ladder construction, 
lioAvever, are equivalent to tho.se of a dredge Avith 18-cu.ft. buckets. As 
the buckets dig the bedrock they are forced into the hard bottom by pres- 
sure of the digging ladder resting npon the backs of the buckets. This 
dredge has the hardest digging of any knoAvn successful dredging opera- 
tion in California. It Avas built upon the site of an earlier dredge of 
much larger bucket capacity Avhich Avas abandoned because it lacked 
poAver and strength to operate successfully. Manganese steel chips from 
the bucket lips are found on the gold saving tables; evidence of the 
tremendous poAA-er used in cutting into the bedrock. 

A recent Yuba development in main drive arrangement provides for 
the use of tAvo a-c motors mounted just aft of the upper tumbler. The 
motors are of equal poAA'er and sufficiently synchronized to operate Avith- 
out trouble. Each motor is connected through V-belts to the pulley shaft 
and the double drive is typical of dredging practice ; pulley shaft pinions 
to intermediate gears to bull pinions to main-drive bull gears. The inter- 
mediates are best if of herringbone type. This type of main drive is 
used on dredges such as Yuba No. 20 at Jfammonton and Capital No. 4 
near Fol.som. each an 18-cu.ft. dredge using two :50()-hp. 440-V motors. 

No great change has been made in the revolving screens used on 
dredges in California. In some foreign fields tAvo or more screens are 
used sometimes but it is California practice to use but one. Material 



.36 



PLACKR MINING KOR GOLD IN CALIFORNIA [Bull. 135 




Sec. I] BUCKET-LINE DREDGING — ROMANOWITZ AND SAWIN 57 

for screen and liner plates has been p:reat]y improved. Early screen 
plates were of low carbon steel ; later of high carbon steel (.40-.50C) with 
drilled tapered holes. Cast man<?anese- steel screen plates with cored 
tapered holes were introduced and improved greatly the life of screen 
plates. One disadvantage was the cored holes ; many operators preferred 
that holes be drilled because a closer spacing could be secured. To meet 
this demand, about 15 years ago experiments were made with U. S. Steel 
abrasion-resisting steel plates. Today many dredge screens have ARS 
screen plates which are taper drilled. As the name implies they resist 
abrasion caused by .sand in the screen ; also, they are hard because of 
chemical content. Cast manganese-steel plates, where subject to pound- 
ing by rocks in the screen, 'work harden' and are preferred by some 
operators. Where no pounding action takes place the life of such plates 
is not longer than AR8 plates which resist abrasive action. Screen 
plates have tapered holes so as to pa.ss all small gravel entering. Hole 
spacing and diameter must be determined by experience to secure best 
results. Plates in different courses of the screen usually differ in hole 
diameter and spacing to secure better distribution through the screen to 
the tables or jigs. 

Gold saving table arrangement has undergone much thought and 
change. Older dredges distributed material, which came through the 
screen, to athwartship sluices which dumped into fore-and-aft sluices; 
two or more of the former emptying into one of the latter causing greatly 
increased volume and greater velocity. Because only a small percentage 
of the cleanup was found in the fore-and-aft sluices, it was long felt that 
practically all of the gold VN^as caught in the athwartship sluices. Even- 
tually it was found that such gold as reached the fore-and-aft sluices 
probably was washed overboard because of the increased volume and 
resulting greater velocity in those sluices. The old theory that greater 
table area contributed to larger savings was upset by the new findings. 
A new practice based on total width of all sluices making up the tables 
and carrying a controlled volume was substituted. Yuba No. 20 at 
Hammonton, when designed and built, had tables and sluices based on 
the new ideas. It and later dredges are arranged so that material from 
the screen can be conveyed from the upper end to any lower position 
before reaching the tables. All gold saving is done in athwartship sluices 
which are fed from head gates in two distributor troughs under the screen 
and extending aft beyond the lower end of the screen. This new arrange- 
ment secures a more even accumulation of amalgam and avoids the older 
system of collecting most gold in a triangular section of forward tables 
near the upper end of the screen. It is found that even with less table 
area a much higher efficiency results. Double-banked tables are often 
used ; the upper about 6 inches above the lower. The top tables are 
provided with counter-weights to aid in lifting them on hinged supports 
to make easy access to the lower tables. 

An outstanding improvement in dredging equipment concerns the 
bucket design and method of attaching lips. Over a long period man- 
ganese steel foundries, making dredge buckets, have worked with dredge 
designers and operators in improving the shape of buckets to secure clean, 
fast dumping. In the past 10 years the lips have been improved to secure 
a firm-locking fit with the buckets and several types of bolted lips have 
been devised and used. The bolted lip, most widely accepted by the 
operators, makes use of two vertical bolts to hold the lip in place on the 



IM.A< FR MINING FOR GOLD IN CAMFORNIA [Bllll. 135 




Perry Idlor. 



bucket ^\•itll tlie ton<rues oi" the lip snugly fitted into recesses in the inner 
walls of the bucket. At one time it -was customary to take five or six 
buckets from the line at each weekly cleanup and send them ashore for 
relippinj; (riveted). Now a lonjr bucket line can be relipped on the 
dredge without removal from the line dm-ing a cleanup period of 4 to 
8 hours. 

As long ago as 19] 2, alloy steels were used on California dredges. 
As dredge machinery became lai'gcr, stronger bucket pins and sliafts 
were retjuired but the dianieters could not always be increased. The first 
full heat of alloy steel sold by a mill to one customer came to Yuba at its 
old Mary.sville plant in 1912. It was nuide to a specification developed 
by the comi)any 's metallurgist and from then on bucket pins have been of 
alloy steels. Today's pins are usually nickel-chromium or nickel-chrom- 
ium-molybdenum steels carefully forged, machined, and heat treated to 
develop full strength and wearing qualities. "Wearing plates for upper 
ttnnblers and idlers are usually of heat-treated forged alloy steels or cast 
manganese steel. Bucket bushings, which are removable, are of man- 
ganese steel and it is customary to have bushings of varying thickness to 
adjust the bucket line assembly as pins, bushings, and bucket back eyes 
wear. The length of a bucket line must be kept about constant and as "the 
line wears, three or more buckets may be removed to shorten the line to its 
proper length. 

T.ower tumblers are of cast manganese steel pressed onto alloy steel 
shafts. Bearing seals of many types liave been tried, all with the intent 
of reducing wear in the journals by keeping out grit. Ladder rollers 
and their bearings are of many types and those under water especially 
are .sealed against intrusion of muddy water. Upper tumblers usually 
are of the one-piece type in California having the body and shaft cast 



Sec. I] BUCKET-LINK DHEnfilNG — ROMANOWITZ AND SAWIN 59 

inte<?ral. Wearinp: plates are bolted in place and are replaceable to 
maintain a fairly constant pitch diameter to match the bncket pitch. 

Dredfje hnlls have received much attention hy desifrners; in early 
days they Avere larf^ely box-like structures of Avood and later steel and 
made of a size sufficient to support the di'edjiing machinery. As dredjjes 
became larprer and heavier it became necessary to fiive a lot of thou<^ht to 
hulls, insurinjr a workable freeboard and stability for the dredjje. Acci- 
dents to hulls sometimes resulted in flooding; and capsizinp-. causinjr j-reat 
dama<?e aiul occasioiud loss of life. Modern dredjje hulls are desi<i'ned 
Avith water-tijiht com])ai"tments usino' every precaution to comply with 
safety re(|uirements. A more modern development led Yuba Mainifac- 
turin<r Company in lO.'i.l to experiment with portable ]K)ntoons for hulls. 
Many Yuba dredges and ])ei'haps others today are e(iuipped with fully 
portable pontoon hulls which form a series of Avater-ti<:ht ccmipartmcnts, 
bolted tofjether and havinj;- strenjith equal, at least, to any so-called 
standard construction. Such hulls are especially adapted to dredfj^es 
which may be moved from one pro])erty to another, thereby making; a 
hifrh .salvage value. The pontoon system of constructing hulls was put 
to extensive use by the IT. S. Navy during AVorld AVar TT as reported and 
pictured in the ]iress and trade journals. 

Deep gi-avels in California fields and in other ])arts of the world are 
being dredged successfully because of tAvo develo])ments of i-ecent years. 
The Perry Patented liucket Idhn- and the Yid^a ^Mud Pumping System 
are jointly res]ioiisible for the success of such dredging. The Perry 
Idler is a cyliiulrical device mounted under the digging ladder in a struc- 
tural steel frame. It supports the bucket line about midAvay in its return 
trip to the loAver tund)ler. This support balances and divides the caten- 
ary into tAA'O parts. For di-edges digging 100 feet beloAV Avater level, a 
Perry Idler is jiositively necessary to insure success. It Avas developed 
by the late Colonel O. li. Perry, a Avell-knoAvn engineer, Avho had much to 
do Avith dredging in Califoi-nia and elscAvhei-e over a long period of years. 
From his experience he recognized the need for such an idler to make 
deep dredging Avith a bucket line a practicable operation. 

Coupled in use Avith a l*erry Idler, deep-digging dredges in Cali- 
fornia use a Yuba Mud Pumping System. Designed to remove silt and 
mud from pond bottoms Avhere accumulations reach a depth of 30 feet 
or more, the system Avas first used on Yuba No. 17 at Ilammonton. A 
more detailed description of the Peri-y Idler and the Yuba Mud Pumping 
System Avill be found in another chapter Avhere an article concerning 
the operation of Yuba Dredge No. 20 is reprinted. 

Space does not permit a long discussion of many points of dredge 
design Avhich need careful attention. The boAv gantry supports the 
digging ladder. The stern gantry sujiports the stacker. The loads and 
suspension points must be carefully calculated. The spud used for dig- 
ging takes the full thrust and its design must be such as to Avithstand 
tremendous loads Avithout failure. Small dredges today ordinarily use 
one spud and move ahead and about the pond by shore lines at the 
boAV and stern. I^arge dredges usually make use of tAVo spuds ; either 
can be used for digging and both used alternately for .stepping ahead. 
The stacker belts of rubber are typical of the California-type dredge. 
Long study by rubber manufacturers has resulted in special belts for 
dredging service; especially non-skidding types, such as American Rub- 



(>0 i'i,A( i;h mininc ioh cold in califohnia [P.iill.l:?o 

her Manufacturing' Company's " rii<ilitniii<: Kibbed," Avliicli minimize 
the tendency of wet rocks to roll backward cau.sin«r unnecessary wear on 
belts, idlers, and other e(|uipment. Kubber also is used in dred«rinpr for 
riffles and sluice liners. Molded solid-rubber i-iffles are used on dred<>:es 
liavinjr a lon<r operatinjr life and despite the liij^h initial cost are economi- 
cal bcause there is practically no wear caused by the abrasive material 
c(»nstantly tlowin-r over them. 

I)re(i;:es in California use and wear out literally hundreds of miles 
of wire rope, liow lines and ladder suspension lines in particular are 
l)ou<rht with len^rth of service in mind. These ropes take severe punish- 
ment and oidy the best quality is advisable. Sjiecial constructions, by 
wire rope mainifacturcrs, have lengthened the life of such ropes and the 
experience gained in dredjre woi-k has been of <:reat value in recommend- 
in? ropes for other services. 

In summarizing: it may not be amiss to speculate ujion the future 
of dredfre construction. The history of placer dredjiin? is one of con- 
tinuous improvement. Accidents have occurred in the ])ast and in almost 
every case have jiointed to an improvement which mijiht avoid a repeti- 
tion of similar accidents. The hunuiu element is always present ami 
lapses of memory or attention on the part of a wiiu'hman or other mem- 
bers of a dredj:^e crew can result in disaster. Dred<ires of the future 
will become more automatic in operation than ever. Trends in dred<,'e 
desijrn today are toward jrreater dependence on electric controls. These 
will relieve the winchman, to a large deforce, of responsibility for maxi- 
mum yardaj?e. high running time, and accidents due to human failings. 
Control devices will j^rovide, automatically, efficient operating si)eeds for 
maxinnnn yardage under all ground conditions, full use of motor capaci- 
ties inuler varying loads, and thereby maintain highest possible running 
time. Some electrical devices now safeguard ma(;hinery against human 
failure. For instance, a "Lilly control'" on a ladder hoist will prevent 
a winchman from dropping a ladder too fast, endangering the motor 
windings and also from raising the ladder too high or droi)ping it too 
far. Improvements, such as are contemplated above, add to the initial 
cost but will more than pay for them.selves in the long run. 

Dredge operators in California have one great advantage over oper- 
ators elsewhere in the world. Our dredging areas are not far from main 
highways and transportation is not a problem. Si)are parts can be 
secured in California on short notice, since the dredge-building industry 
centers in the San Francisco Bay area. New ideas can be tried in the 
field and builders of dredges can easily get back and forth from dredges 
wliile watching new developments. It is not necessary to experiment 
at tlie customer's expen.se in a far-otf country and wait months for a 
report. The success or failure of newly designed e(piipment is soon 
known to the dredge builder. This fact has helped in making California 
the cejiter of the j)lacer dredge l)uil(ling industry. 

Dredging in California for gold is in line with the State's heritage. 
California got its fast start toward statehood because of gold mining 
and all through its history, gold has been a mainstay. There is a theory 
that basic industries are tho.se which can ojjcrate successfully and .ship 
their products from the point of production profitably; thus considered, 
gold dredging is a basic California industry and can continue to be one 
in the future. 



BECKER-HOPKINS SINGLE-BUCKET DREDGE 

Hv If. A. Sawin • 

A new type placer dredge, known as the Becker-IIopkins Single- 
Bucket Dredge, was introduced prior to the war. Its inventors are G. E. 
Becker and II. II. Hopkins of San Francisco. Yuba Manufacturing 
Company acc^uired manufacturing and sales rights under the Becker- 
IIopkins patent. liecker-IIopkins dredges are 'single-bucket' exca- 
vators; each dredge being a self-contained floating unit, designed par- 
ticularly for operation on shallow properties, in limited areas, or in nar- 
row canyons. Avhere it is impracticable to operate bucket-line dredges or 
other types of equipment to advantage. 

The digging unit of a Becker-IIopkins dredge consists of a bucket, 
built integral with a sluice-type boom, which conveys dredged material 
from the bucket to the screen. The dredge operates from a fixed posi- 
tion on the pond surface, being moored by bow and stern lines. The 
bucket is dropped vertically at the rear end of the well and a cut made 
horizontally by pulling the bucket forward into and through the material 
being dredged. The telescoping boom extends in length automatically, 
permitting a horizontal bottom cut. When the bucket reaches a point 
under the bow of the dredge, a latch is released and the bucket is elevated 
radially to a point where the dredged material slides down the sluice- 
type boom and is evenly distributed to the screen. 

Boulders can be successfully dislodged and in many cases put 
through the screen and disposed of over the stacker. Boulders too large 
for the bucket can be brought to the surface and cast aside by use of a 
tractor, usually available on dredging properties. The ready control, 
Avhich the operator has of the sluice-type boom, makes it possible for him 
to slide a boulder into the screen gently ; this avoids wear Avhich might 
result from dropping heavy boulders at high speeds. Control of the 
slope of the boom also prevents heavy intermittent overloading of the 
.screen, even distribution being as.sured because the movement of dredged 
material down the boom can be accelerated or retarded. 



Sales Engineer, Yuba Manufacturing Company, San Francisco, California. 




Fio. 2" TJfckcr-IIopkins sinple-biieket dredge. 
( Gl ) 



62 



ITACFH MiNiNi; idK <:()].]) \s CALIFORNIA [Bnll.THo 




Fig. 24. Bucket detail, Becker-Hopkins single-bucket 
dredge. 



Each cut follows the previous cut, until the desired depth has been 
reached. The horizontal cutting action is controlled, which makes it 
possible to clean bedrock thoroughly. The dredge is moved to new dig- 
ging i)ositions on the pond by use of the sidelines, and from its new posi- 
tion, the digging cycle starts again. 

This is a brief description of the digging operations of Becker-IIop- 
kins Single-Bucket Dredge. The other functions of dredging are similar 
to tho.se on a bucket-line dredge. Power can be either electric or Diesel 
engine to suit conditions, and all units are made for easy dismantling, 
shipping, and re-erection. 

The original designers built and ojierated a small unit in California 
in cooperation with A. R. McCJuire of Fresno. Later, Mr. McGuire was 
interested in the operation of two such dredges (a 1-cu. j'd. and a 2-cu. 
yd.) in Alaska prior to the war. Just before the war, Yuba built its 
first one for use on Butte Creek in Butte County, California. Experi- 
ments with it demonstrated worth-while qualities but also pointed to 
several 'bugs' which resulted in design changes to improve its operation. 
War conditions closed down the work but as this is written (January, 
1946) the dredge is being rebuilt on a property in Yuba County and it is 
planned to operate it experimentally for several months to test the new 
design. 



JIGGING APPLIED TO GOLD DREDGING * 

r.v 1'. Malozkmofk** 

Ji^jrin<^- is one of the oldest processes used by man in separating the 
heavy minerals from the lijrliter ^rangue. At the turn of the present 
century it was extensively used for the concentration of base metal ores 
and for the washing of coal. Comparatively recently it has been widely 
applied for treating placer gravels in recovering tin, tungsten, and gem 
stones. 

Its extensive application for the recovery of placer gold is of even 
more recent origin. One of the earliest large scale jig tests on board a 
gold dredge was made by J. W. Neill in 1914 on the Yosemite dredge in 
California.^ Subsequently, tests were made by the Natomas Consolidated 
Company, also in California. This company used Neill jigs in fore-and- 
aft sluices in an effort to effect a saving of some of the gold that was 
being lost in the tailings. 

However, these were isolated examples for some twenty years, until, 
in 1932. the Bulolo Gold Dredging Company initiated a series of thor- 
oughgoing tests, as the result of which one of the company's dredges in 
New Guinea was completely equipped with an installation of Bendelari 
jigs. This installation proved the practicabilitj- of treating the entire 
output of the dredge (screen undersize) with jigs, and the companj^ took 
steps to prepare for extensive application of jigs on their boats. The 
company's engineers soon designed a new machine, now- know-n as the 
Pan-American Placer Jig, in the effort to make a jig particularly adapted 
for use on board the dredges. Subsequently, several more boats in New 
Guinea and in Colombia were equipped with jigs of new design. As the 
result of the success of these installations, interest in jigging on board the 
dredges was again aroused in the TTnited States, and in 1936-37, instal- 
lations were made by the Yuba Consolidated Goldfields, Ltd. in Cali- 
fornia, and by Fisher and Baumhoff in Idaho. Of recent months several 
other companies are reported to have made jig installations on their 
dredges. 

These efforts may well mark a turn in the history of gold dredging 
industry, spelling, as they do, the directing of attention tow^ards improv- 
ing the gold recovery by the elaboration and refinement of the gold saving 
practices on board the dredges. Not that efforts in this direction were 
lacking in the past, for great improvements in the design of riffles and 
their adjustment were made ; but riffles obviously have their metallurgical 
limitations, especially under the conditions imposed by dredge practice. 
Jigging, on the other hand, is free of some of these limitations, and, if 
properly emploj'ed, capable of meeting even the more exacting dredge 
conditions successfully. Jigging on board the gold dredges is a modern 
development in dredge practice that no operators can afford to ignore, 
and one, it seems safe to predict in the light of the interest already 
aroused, which is destined to gain almost universal application in the 
very near future. 

Now that the groundwork has been laid, and jigs on dredges, when 
properly installed, have been proven beyond any reasonable doubt to be 

• Written for and published as pamphlet by Pan-American Engineering Company, 
820 Parker Street, Berkeley, California. Printed in condensed form in Engineering 
and Mining Journal, vol. 13S, no. 9, September 1937. Reprinted by permission of Pan- 
American Engineering Company. 

•• Formerly metallurgical engineer for Pan-American Engineering Company. 

1 Neill, J. W., Application of jigs to gold dredging: Min. and Sol. Press, vol. 109, 
p. S39, November 2S, 1914. 

(63) 



G4 TLACKK MINING KOR GOLD IN CALIFORNIA [Bull. 135 

botli prufticahle and profitable, tlic time seems propitious to rehearse for 
tlie benefit of the teclmieal fraternity the advantages that jigging on 
board the dredges otter, and the problems that will eonfront the operator 
who contemplates an installation of ji;.'s. 

The subject is so vast and its ramifications are so numerous that it 
would be impossible to deal with it in detail within the scope of a single 
magazine article. The main imrpose of this paper, then, is to define 
the problems involved in <rcnci-al tei-ms so as to jn-esent an introduction 
to a subject that is both timely and little known. 

The use of jigs on dredges will be considered only because of their 
ability to effect a saving of <>old in addition to that made by the riffles. 
That losses exist when riffles only are employed is recognized by every 
intelli]L'ent dredge operator; and despite exhaustive efforts towards 
improving' riffles and other conditions on a dredge, appi'eciable losses are 
ever j)res('nt in the majority of ca.ses, {ireater in some than in otliers, yet 
usually of sufflcient nui^nitude to warrant serious consideration of some 
other means of reducing these losses. The gold lost by the riffles is 
j)red()minantly fine, althou^'-h sometimes it might be comparatively coarse 
if ffat and difficult to amalgamate. The j^resence of "rusty" gold in the 
ground is usually indicative of appreciable losses, for it is a general con- 
tention amonji: placer o])erators tluit the gold wliich does not amalgamate 
or anudgamates only with difficulty, such as "rusty gold," is difficult to 
save by the riffles. 

Limitations of the i-iffle as a gold saving device are inherent in it: 
its action is such that the gold must settle and be entrapped by the riffle 
in a swift cui-rent of water, the velocity of which must be great enough 
to transport the material, both coarse and fine, across the riffles. The 
less the velocity of the current of water, the greater is the tendency of 
the gold to settle and be saved by the riffles, yet at the same time, the less 
the carryiu'; power of the water stream; and con.setpiently the yardage 
cajjacity of a given area of riffles is reduced. Since space on the dredges 
is limited, only a certain limited riffle area is available for a given 
yarda<re to be handled by a dredge. In the effort to increase the output 
of a dredge, the yardage is often boosted beyond the optimum capacity 
of the available sluices, aiul the amount of water and the slope of the riffles 
is so rejrulated as to induce sufficient velocity of water to transport all 
the material; the recovery of the gold will naturally suffer under such 
conditions. Still other factors, such as packin<; of the riffles, esjiecially 
with lieavy black sand, and siulden surges in feed which tend to- dislodge 
aiid wash out the gold that has already been entrapped by the riffles, 
are all inimical to tiie optinuim recovery of the gold, and can not always 
be fully corrected. 

The action of the jig, on the other hand, disposes of several factors 
tliat cause loss of «rold in the riffles. The jigs operate continuously, and 
the bed can be adjusted so as to permit settling and, consequently, 
trai)ping of the gold at all times. Once trapped, it is removed from the 
stream and there is no more daufrer of losing it as there is in riffles that 
pack, or from which gold is dislod«red and washed out because of occa- 
sional sur;,'es. The j)icsencc of a larjre amount of black sand in the 
ground, which causes especially severe packing of the riffles and conse- 
quent loss of gold, will not cause lo.ss of gold by jigs. Furthermore, dilu- 
tion of tlie feed to the ji«rs need not be so great as to the riffles, since in 
the case of ji};s the transporting' of the nuiterial is aided by the alternate 



Soc. J] .ii(:(!iN(! Ai'i'Mi:i) TO (i()r,i) dukixunc; — MAii()Zi:i\r<>i'i' 05 

l)ulsati()iis, whereas the earryinj:: power of Avatcr is the sole transporting 
ajreiicy in the case of riffles. For tliis reason tlie conditions on top of the 
jifX bed can be made far more (piieseent than for riffles, thns affording a 
better opportunity for tlie gold to settle. 

Natnrally enough, the jig has its limitations also. It is only a grav- 
ity machine, therefore will recover only that gold which will settle by 
gravity under the conditions that obtain on the jig bed. Some of the fin- 
est gold will be lost by the jigs as well, but at the present stage of develop- 
ment of the arts of the recovery of gold, this loss is in almost all cases 
below the economic limits of the known methods. 

P^lotation, for example, can probably be applied in some form or 
other for the recovery of the fine gold that \yill be lost even by jigs, but the 
cost of doing so, it appears at present, will come very close to, or exceed 
the amount recovered. In 1!);^;} an installation of six full size flotation 
machines, which treated ']()() tons per day, was made on one of the dredges 
operating on the American River in California.- Three months' opera- 
tion showed that the recovery of gold by flotation from the sand wheel 
overflow, which should contain the bulk of the finest gold in the dredge 
tailings, was only 2 to 5 cents per ton on heads of 3.5 to 9 cents per ton, 
as calculated from the concentrate and tailing assays. An average of 
120 assays made on the flotation heads directly gave a value of only 9.3 
cents per ton ; each assay was made on six to eight assay ton charges. 
These values are based on $35.00 gold. 

Besides, it must be remembered that all placer deposits were formed 
as the result of the material settling by gravity, and in most of the placer 
deposits now being exploited the finest gold had already been eliminated 
by natural agencies during the process of deposition, except in rare cases 
in which the conditions of deposition w^ere such that even the finest 
material settled and formed the deposit. For this reason there will be 
very little gold that cannot be recovered by gravity, provided the 
method of recovery is sufficiently refined to reproduce the settling con- 
ditions that obtained during the formation of the deposit, when material 
settled by gravity under natural agencies. 

There are, of course, some exceptional deposits in which the gold 
has been liberated by chemical agencies from the. gold-bearing sulfides, 
or those in which the gold is still locked up within the sulfides or oxides 
that have been deposited with the sand and gravel comprising the deposit. 
Such occurrences of gold present individual problems that involve meth- 
ods of milling in one form or another for their solution and will not be 
considered in the present paper. 

The use of jigs for the treatment of placer gravels presents problems 
some of which are entirely different from those encountered in the use 
of jigs in milling in the concentration of base metal ores. In the base 
metal ores the ratio of the specific gravities of the valuable mineral to 
that of the gangue is relatively low; for this reason, and in order that 
the jigs make proper recoveries, it has been general practice to classify 
the feed as to size rather closely, and to provide a jigging surface that is 
much longer than it is wide. 

In placer gravels, on the other hand, the ratio of the specific gravities 
of the gold to that of the sand and gravel to be discarded is very much 
higher than for base metal ores. Close classification of the feed, though 

-A. test made by the Pan-American Engineering Corporation, Ltd. 



Gf) vL\n:n minixc ioh cold is CALiroRNiA [Bull. 135 

(It'sirablf. is nut so cssi-iit i;il. iior <l'»fs llic i-atio of Iciif^th to widtli of 
ji^'^;i^^r surfat-o need he so -rcat. Accordin-rly, the load i)er s(|iiaro foot 
of jip<riii^' surface can be niatei-ially increased without ai)precial)ly att'ect- 
int,' the residts that cau he ohtaiued. 

This is fortunate, for wow it not so, ji^jriuji: as practiced in metal 
mininj: industry couhi hardly have h(>en ai)plied to the p:old dredfres. 
Close chissification of the screen undersize on the dred^^e would iu)t be 
practicahle; and floor space is always at a.preniiuin, thus requirinjr the 
ptld saving' iuacliin(>ry on hoard the drcd^ic to have lai'fze capacity ])er 
unit of floor space. 

When attention turned to ji<rs to he used for dredges a <rreat many 
different desijrns of jijrs u.sed in washinj; of coal and in coiu-entration of 
hase metal ores were available, but none of them were desi}rned to conform 
to the altojrether peculiar conditions imposed by the <i:old savin-:' dredjre. 
For the most jiarf. the jijrs were heavy and cumbersome. occui)yin<;- con- 
siderably more space than is i-eipiired by the elfective jie-giufi- area. One 
of the first ji<:s tried out on a <rold di-edpe. the Xeill f)i<i, conformed to 
the demand for economy of floor spat-e and total room occupied was con- 
fined to the screen area of the .jijr;zinjr surface. 

The first modern ji^r ap])lied to <rold di-edjj:es was the Bendelari Jifjj, 
wliich actuated the water throuj.:h the screen and bed from below by 
means of a i^lunjrer sealed with a rubber diaphrajiin. This permitted 
the floor spac(; to be defined by the screen area of the ji^'. 

Somewhat later a new ji'/ was desijiiied by the Placer Develojunent 
Coni|)any's cnjrineers and used with success in New (luinea at the liulolo 
(ioldfields. In this ji<r. now known as the I'an-Amei-ican Placer Jipr, a 
jKirf of the hufi-h in tlie form of an iiivei-ted coiu^ is moved by means of 
an eccenti-ic to transmit the ])idsations thi-oujih tiie bed. Free discharge 
of eoiiccjitrates and unifoi-m disti-ibntion of ])ulsation througlumt the 
area are thus aided. The weight of the machine was cut down to tlie 
mininnnn to meet the demand of the dredges, especi;dly the smaller ones, 
for least weight of the gold saving e(juii)ment. 

In jirinciple. these modern jigs are no different from the old type 
machines, such as tlie Ilarz Jig. To secure activation of the bed the 
water pidsation is transmitted mechanically by means of an eceentrie. 
In the Harz this was done by a phniger working in a separate water com- 
partment outside the Initch ; in the Placei- .lig this is done by a moveable 
cone-shaped hutch, and in the IJendelai-i by a diai)hragm inside the hutch. 

Jigs foi" gold ]ilacer operations ai"e designed so as to i)roduce the 
concentrate continuously as a hutch product. A certain amount of shot 
bedding is usually used to reduce the amount of concentrate thus 
obtai?ied. It is (piite inii)ortant to have delicate control over the suction 
so as to be able to seciu'e maximum recovei-ies with the maximum ratio 
of concentration. This reipiirement was answered by a Initcli water 
connection closely coidrollcd by a i)lug cock. A screen area of 42 by 42 
incites has become largely standard for the jigs used on dredges. 

Testing of Dredge Tailing Losses 
Eveidually, perhaps, it may be found that all gold dredges that 
employ riffles .shoidd install jigs to improve the recovery of gold. But 
because jigging on dredges is a comparatively recent development, and 
data on wide variety of dredge operations are still lacking, such a gen- 
eralization is prematm-e. Hence, whenever a jig in.stallation is eontem- 



Sec. I] .HGfllXG APl'LIKI) TO GOLD DKKDGINCi MAI.OZi;>[OFF 07 

plated, it sliould riglitly be preceded by suitable testing, which can 
definitely prove that the jigs are capable of eflt'ecting a recovery in addi- 
tion to that obtained by the ritlles. 

The existence of dredge tailing loss may be (jualitatively detected 
with relative ease, yet to arrive at a definite, reliable figure in cents per 
yard is an extremely difficult task. The difficulty of this problem will 
readily become apparent if the factors that complicate such a determi- 
luition are considered. 

The values recoverable by jigging from dredge tailings are usually 
vei-y low, in the majority of cases less than 5c per yard ; the gold is free 
and not uniformly distributed; so that even if a very large sample of 
several tons be taken the sample would hardly be representative of the 
dredge operation as it is conducted from day to day. Anyone acquainted 
with the dredging operations is familiar with the fact that the gold 
usually occurs in the ground in "pay streaks" of comparatively small 
thickness, and before the "pay streak" is dug a large proportion of the 
total digging time is consumed in moving material that is barren or nearly 
barren. Thus, even the most elaborate intermittent sampling will almost 
always be open to doubt. 

However, a quantitative determination of the sluice tailing losses can 
be made accurately by detei-miiiing the gold content of a small, con- 
tinuous cut of the total flow of the tailings ; such for example, as con- 
tinuous jigging of the total flow of one tailing sluice, or of a stream 
representing a small j^art of the total dredge tailing flow. 

Numerous methods can be applied for this purpose; a fairly com- 
prehensive discussion of them and of the interpretation of the results 
is beyond the scope of the present paper. The subject is sufficiently 
broad to merit its presentation in a separate, full length paper. 

Suffice it here to say, that a reliable determination of the dredge 
tailing losses is possible, and should be made for the border line cases, 
in which it appears that the existing loss is small and may not be suffi- 
cient to justify the use of jigs. 

Besides the determination of the amount of gold that can be saved 
by the jigs, testing may at times be required for other purposes. For 
example, a special method of treating the rougher concentrates may be 
found neces.sary, especially when the ground to be dredged contains a 
large amount of heavy mineral constituents, such as black sand and 
P3'rite ; or, again, when a part of the gold in the ground is present in the 
form of included values within the heavy mineral constituents. In 
these cases large scale testing on the dredge may be necessary in order 
to be able to devise a suitable method of treating these concentrates for 
the final recovery of the gold. 

Factors Affecting Jig Installation and Jig Recovery 

The nuinber of jigs necessary, the manner in which they are installed, 
and the method of treating the rougher concentrates will depend on a 
large number of local conditions that will vary widely from one operation 
to another. A few of the more important ones are : total yardage dug ; 
proportion of screen undersize to oversize ; ease with which the ground 
is disintegrated and washed, which in turn may determine the dilution 
of the feed to the jigs ; the nature of that feed ; and the nature of the 
gold, i.e., whether coarse or fine, flat or granular. 



(is I'I,A( I.K MISINC lOK COM) IN ( AMIOHNIA (r.nll.1.^5 

Altlu.u^'h till' Tin'cliaiiical capafity of a 42 by 42-inch jig has been 
established at abont :iO cubic yards per hour, the etTect of some of the 
above factors may necessitate a radical revision of this figure. It needs 
be reduced for sandy ground, when excessive dilution obtains, or when 
fine, flat gold is i)resent. At times it may be possible to rate the capacity 
of the jigs to fit the conditions that obtain when the dredge is digging 
j)ay gravel, even though they will be overloaded when it is digging the 
top ground, wliicli may contain a greater proportion of sand than does 
the pay gravel. As long as this material contains little or no gold no 
harm will be done. 

Excefisive dilution of the screen undersize will usually mean exces- 
sive top water velocity over the jig bed, and will cause the loss of fine 
gold that does not have a chance to settle in the swift current. When 
this excessive dilution cannot be reduced because the ground requires a 
large amount of water for proper disintegration and washing of the ma- 
terial in the screen, the jigs should be rated at a lower capacity than nor- 
mal and some means of controlling the velocity of the top water across the 
jigs should be provided; boiling boxes or retarding baffles are the usual 
remedy. Another method to obviate this difficulty is to dewater the 
entire jig feetl, or some part of it. Although this may not always be 
j»ossible, it will always be desirable. Dewatering elevators, dewatering 
tanks or sumps may seem a revolutionary, complex innovation on a 
dredge, but it is one that can certainly be justified when jig recovery 
can thereby be appreciably increased. 

After the jigs are properly installed, there is yet their adjustment 
to make, which is a problem that is at times quite complex. The material 
passing through the dredge screen from hour to hour is generally variable 
to the extreme, both as to quantity and character. Since the amount of 
water added to the screen will usually remain constant, with the variation 
in the quantity of solids delivered to it, the dilution of the screen under- 
size will vary in inverse proportion. Because of the variation as to 
(piantity and dilution, the distribution of the load fore and aft will 
change con.stantly. Moreover, the list of the boat from side to side, and 
the pitch fore and aft will att'ect the distribution of load accordingly. 
These difficulties, more serious on the small dredges than on the large, 
may be overcome to some extent by a carefully considered installation, 
and by an adjustment of jig controls that would permit effective jigging 
even at the worst of conditions. This, however, would only be a com- 
promise and would never be altogether satisfactory, since under other 
conditions that would obtain sucli adjustments may not be the optimum. 
The only etTective remedy for aggravated cases of this sort is the instal- 
lation of a central distributing system, which would consist of a central, 
preferably mechanical, distributor, to which the entire ])roduct from the 
screen is delivered, and from which the load is equally distributed among 
the several jigs installed on the boat. 

Jigging Practice 
Jigging practice consists of several different operations. The first 
is the roughing treatment by one row of jigs on each side of the dredge 
screen. This is usually followed by a second treatment over the scavenger 
jigs. The scavenger jigs are necessary to assin-e the more complete 
recovery of the fine gold. Only in special cases will it be possible to limit 
the operation to a single treatment by one row of jigs : such, for example. 



See. II .II(i(iIN(i AI'l'MKO TO (!<)IJ) DKKIKiINC SI \L0'/A:UC)V'V ()9 

ill wliic'h only a small proportion of the total f;old in tlie g:round is fine; 
but wlien the <j:o1(1 to be reeovered is jiredominantly fine, the number of 
jips installed has to be increased so that each is required to treat con- 
siderably less than its normal rated capacity. 

Besides the roujrhinfr and scavenp^inf? some method of treatment 
of the rougher and scaven<rer concentrates must be provided for. Gen- 
erally, the feed to the jifrs, depend in«; on the size of the dredge, will be 
from 100 to 400 cubic yards per hour. The ratio of concentration that 
can be achieved by rougher and scavenger jigs will on the average be 
100 :1. This means that from 1 to 4 cubic yards of concentrate per hour 
must be treated for the recovery of gold. Obviously, this cannot readily 
be done by batch treatment but must be done continuously. 

There are two methods that have been developed for this treatment: 

(1) The concentrates may be treated directly for the recovery of 
gold by grinding in the ball mills in the presence of mercury and then 
passing the resulting product over amalgamation plates. Grinding need 
not be very intensive, as the polishing of gold and its ready amalgamation 
is the main purpose of such treatment. 

(2) Another method, which is the simpler and therefore the prefer- 
able one, is to pass the rougher concentrates over suitable cleaner jigs in 
order to reduce the amount of the final concentrate to be treated for the 
recovery of gold. Of recent months a hydraulic jig known as the Pan- 
American Pulsator Jig, has been used for this purpose to an advantage. 
It allows the production of a cleaner concentrate that bears a ratio of 
1 :30 to 1 :100 to the primary concentrates. The final concentrate is thus 
reduced to a small bulk that can be readily amalgamated in batches, as 
in an amalgamating barrel, and the amalgamated product either rejigged 
or streamed down for the recovery of mercury and the contained amal- 
gam. With this method, the loss of gold in the intermediate products 
that are discarded is negligible. 

With different combinations of the two methods a large number of 
variants can be had. For instance : the primary concentrate may first 
be rejigged, then the resulting cleaner concentrate subjected to continu- 
ous or intermittent grinding in the presence of mercury, and finally 
passed over a trap and an amalgamation plate for the recovery of the 
mercury and amalgam. The obvious advantage of such a procedure over 
the direct grinding and amalgamation of the primary concentrates is 
that the size of the grinding installation can be only one-thirtieth to one 
one-hundredth of that necessary for direct treatment. 

Installation 

Various methods of applying jigs to existing or proposed dredges 
may be employed. They can conveniently be grouped into two classes : 
(1) installing jigs as auxiliary recovery equipment, conforming to the 
existing sluice layouts ; (2) installing jigs as essential recovery equipment 
which may or may not entail the elimination of the existing sluices. 

When jigs are installed as auxiliary recovery equipment they may 
be placed either in the fore-and-aft sluices or at the end of the lateral 
sluices as is shown by the accompanying figures 25a and 25fe, respectively. 
When in fore-and-aft sluices, as in figure 25a, the jigs will probably be 
required to take more than their share of the load because the amount of 
material that these sluices usually handle is greater per inch of width 
than it is on the lateral tables. Also, because the riffles require more 



70 



ri-.\( i:i{ MININC lOK (Kllil) IN CAMFOKNIA [l-5ull.l3o 



HS 






^-LATERAL SLUICES 



ROUGHER JIG 

SCAVENGER JIG 






m- 



FORE t AFT SLUICES 



1 


^ 


X 


1 


X 


X 




X 


V 








)^ 


X 


y^ 




























X 


V 


V 




y 


^ 


X 


V 




X 


9r 1 


1 











ii< 


ii 






8§; 


^I§ 

























III 








SHH 




^^^ 















Km. 25. JiK arrangement.s: four imthods of aiJplyiiiB jigs on gold dredges, 
o. Jigs instnlled in fore-and-aft sluices; b. jigs installed at end of lateral sluices; c, 
jig-H in.stalled in lateral sluices, preceded by short .sections of sluice; </, jigs installed 
In lateral sluices, next to the screen. 



Sec. 11 JIGGING APPI/IED TO GOLD DREDGING — MAIiOZHMOFF 71 

Avater tlian is best for jiji'jiinjr there Avill always be excessive dilution 
impossible to reduce, and consequently, an excessive velocity of top 
water that will be difticnlt to control, liesides, headroom will be limited 
at this jioint. 

Wlien installed at tlie end of the lateral sluices, as in figure 25&, 
the load over the jigs will usually not be excessive, as the width of the 
total jig installation will be equal to the Avidth of the total table area. 
But here again, excessive dilution and velocity of top water obtain, and 
headroom is not always available. 

Either one of these methods recpiires a double clean up. The sluices 
ahead of the jigs will recover the major pro])oi'tion of the gold and must 
be cleaned up every so often ; the jigs will yield an additional amount that 
is cleaned up continuously aiul therefore separately from the major 
riffle clean-up. 

It would therefore seem preferable to install the jigs as close to the 
screen as is possible, so that they may constitute the essential recovery 
equipment. In this location dilution of the feed can be more closely con- 
trolled, the headroom is almost always available and only a single clean-up 
is necessary. If riffled sluices are contemplated below the jigs they will 
have a much better chance of doing good work because the jigs will 
remove the heavy mineral constituents which are such a source of trouble 
in packing the riffles. Figures 2.10 and 25c/ show a possible method of 
installing jigs as essential recovery equipment. The jigs may or may not 
be preceded by a short section of sluices, the main purpose of which 
would be to distribute the feed uniformly across the width of the jigs. 
These short sections of sluice may also be riffled and made to trap out 
coarse gold and tramp iron. The installation of jigs in this position will 
not necessarily involve the scrapping of existing sluices, as the jigs may 
be cut into them. 

Although at present the installation of jigs on a dredge will be con- 
templated only if the jigs can be shown to produce greater recovery of 
gold than the existing riffles, the time may not be far distant when it may 
become recognized that the jigs offer sufficient other advantages to be 
installed even when they do not yield increased recoveries of gold. As 
mechanical improvements of dredge machinery are made, the percent 
lost time owing to repairs will decrease, and the periodical clean-ups of 
the riffles may necessitate loss of operating time in addition to that due 
to dredge repairs. This obtains even now in a great number of dredge 
operations. With proper jigging installation it may not be necessary to 
have any riffles on board the dredges at all, consequently the entire 
clean-up can be effected continuously, involving no loss of time. There 
is no reason for the jig repair to be responsible for any appreciable loss 
of time, since, if properly cared for, they can be made to operate almost 
Avithout interrujitious. In milling, which employs similar machinery, 
it is not- unusual to have 98 to 99 percent operating time year in and 
year out. 

This paper is tin- (nit;;ro\vth of some of the work done by the Pan-American 
Enffineerinj; Compiiiiv at the instance of the Placer Development Company, Ltd., Yuba 
Consolidated fJold Fields, Ltd., and Fisher and Raumhoff, to which companies credit 
is due for initiating' the installation of .iijjs on dredges recently. Their cooperation in 
that work, which made the writing of this paper possible, is gratefully acknowledged. 
Also, the writer wishes to acknowledge with thanks the helpful guidance given by 
V. E. Bramming and F. "W. Collins. 



72 



.CKK MlNINCi 1-OK OOM) IN CALIFORNIA [Bull. V.\r, 




NOTES ON JIGS FOR GOLD DREDGES 

By p. W. Collins* 

The article Avritten by P. Malozemoff entitled Jigging Applied to 
Gold Dredging and published in condensed form in Engineering and 
Mining Journal, vol. 138, no. 9, 1937, is a very well considered paper, and 
it is reprinted in full above. This paper of Malozemoff 's shows the pic- 
ture as it was late in 1937, and since then a great deal of detailed informa- 
tion has been developed that was not then available. High points of 
these developments are briefly outlined below. 

Methods and equipment have been developed for testing tailing from 
existing dredges to determine the amount of gold present that can be 
recovered by jigs. Figure 26 shows one of these testing sets. The 
method is to cut a sample of about 2 cubic yards per hour from one or 
more tail sluices and this is fed continuously to the 10 by 60-inch 
rougher-jig. The tailing is measured to determine volume treated and 
the rough concentrate is jet-pumped through a rubber hose to the dewa- 
tering cone ahead of the cleaner-jig. The overflow from the cone goes to 
the pond and the underflow to a 12-inch Pulsator jig. The photo shows 
a 12-inch single-cell jig, but a two-cell jig is usually used. The cleaner- 
jig concentrate is amalgamated. A number of dredges have been remod- 
eled to use jigs after being tested with this equipment and results to date 
indicate that the test results are reliable. 

From 1932 to 1936 the trend was to install jigs as scavengers follow- 
ing conventional riffled sluices but the error of this is so apparent that 
now the jigs are being installed as close as possible to the screen and are 
depended on entirely to save the gold. However, it is desirable to have 
each rougher-jig followed by a sluice 3 or 4 feet long and as wide as the 
jig. This sluice should carry burlap under expanded metal and its pur- 
pose other than carrying the tailing to waste is to act as an indicator of 
the work being done by the jig. If any gold shows up in the burlap then 
the dredge master should check up on the jig-operators. 

The distribution of the feed to the rougher jigs is of prime impor- 
tance and this has been worked out in a very satisfactory manner along 
lines first developed by Natomas Company. The distributor immediately 
below the screen is made as a modified Jones riffle and automatically 
makes a 50-50 split of the screen undersize to the two sides of the boat. 
It may then go directly to the jig opposite its point of exit from the split- 
ter or be discharged into a fore-and-aft distributor sluice. There is one 
such distributor sluice on each side of the boat and any material in these 
sluices may be fed to any jig aft of the point where it enters the sluice. 
As the major portion of the fine material tends to come through the screen 
near the forward end, this system permits the fine material to bypass the 
forward jigs and reach those farther aft that would be 'starved' if their 
feed carried only that part of the fines that comes through the lower part 
of the screen. 

The attached flow sheet is for a 9-cu. ft. (nominal size) dredge that 
normally digs about 11,000 cubic yards per day and has dug 13,000 
cubic yards in 24 hours on several occasions. The screen openings are 
half an inch in diameter, and about 50 percent of the bank run is under- 

• Mechanical Engineer, Pan-American Engineering Company, 820 Parker Street, 
Berkeley 2, California. 

( 73 ) 



74 



IT.ACKK MIX INC 1X>!{ nOI.l» TN" CALIFORNIA 



[r,ull.l:r) 




Fio. 27. liiiUKl 



size. The pumping of the rou^hei-jiji- coiu-entrate i.s iieeessai-y on this 
partieiilar boat but can be avoided in some cases. A mechanical dewater- 
inp: device for the rou«iher-ji<:: concentrate is more desirable than the 
settlinjr tank shown on tiie flow sheet. 

Placer-type jijzs or similar machines art' always used as rou^diers 
and in such fields as Ilannnonton and Xatomas where the 'black sand 
load' is comparatively li<rht they may also be used as cleaners but when 
the deposit to be dred^^ed carries a considerable (juantity of lieavy 
material the Pulsator jipr should be used for this purpose. 

Two systems of recovering: the jrold from the roujrher-jip: concentrate 
have been develo]ied and are in use on a number of dredjres. The first 
is to pa.ss the rou^dicr-jip: concentrate directly to 'aup:er liole' riffles, which 
amaljramate the clean {rokl. Tails from these riffles are dewatered and 
fed to a cleaner-ji^^ which makes a tailinj; and a concentrate. The con- 
centrate fjoes to a small jrrindinp: mill, and it is jireferable to dewater 
ahead of this mill. The mill-discliar^e «;oes to another set of 'auger 
hole' riffles and then over a scaven^^er jijr and to the pond. The scav- 
enfrer-jig concentrate may be returned to the grindinjjr mill for a short 
time but the circulatin<; load of 'tramp' iron soon builds up to a point 
where it becomes necessary to remove this concentrate and clean it up 
by hand. 

The second system is as shown on tlie flow sheet of the 9-cu. ft. dredge 
above mentioned and involves the use of a Titan Amalgamator. Of the 
two systems the oin* with the Titan Anuilgamator seems to be the better 
and will probably eventually supersede the other sy.stem entirely. 

On two dredges where the gold is very badly tarni.shed the arrange- 
ment has been modified as follows: The cleaner-jig concentrate goes 



Sec. I] 



NOTES OX JIGS FOR GOLD DREDGES COLLINS 




g «n <o K COO) 



l'LA( T.U MtNlNc; I'OH (iOhD IN CALIFORNIA 



[P,ull. 13: 




Fig. 29. Sanrt-drag, Summer X'alley DrtdgiriK Company, Sumpti 



directly to a Titan Amalgamator which discliarj^es to a mechanical 
dewateriiip: device which feeds a 2- hy 4-foot ball mill. The ball mill dis- 
charjies to a second Titan Amalframator wliich is followed by a 12-inch, 
two-cell scaven<,'er jijr. This lias worked extremely well, bnt the same 
resnlts conid probably have been obtained had the cleaner-ji<r concentrate 
been dewatered and jTround, then fed to one amal<ramator followed by a 
scavenf^er ji<;. 

The last dred^re to be remodeled of wliicli we have aiiy record is the 
H-cn. ft. boat of the Sumpter Valley Dredfring Company at Snmpter, 
Ore-ron. This job as remodeled started np in July 1940. The tlow sheet 
is identical with the one shown excepting that a sand-drag is used to 
dewatcr the rougher jig concentrate. Figure 27 shows a 4-cell block of 
i-ougher jigs and figure 29 shows the sand-drag used on the Sumpter 
Valley job. 



TREATMENT OF BLACK SAND 

Black sand accumulates as a concentrate in the riffles or jigs used 
at placer mines to catch the gold. It occurs also as a natural concentrate 
on many of the ocean beaches of California. Under the sundry civil act 
approved Marcli 3, 1905, Congress directed the U. S. Geological .Survey to 
investigate the useful minerals contained in the black sands of the Pacific 
slope, and this investigation was subsequently enlarged to embrace the 
United States. Most of the samples collected were concentrates from 
the sluices of placer mines, but samples from the beaches near Crescent 
City, Upper and Lower Gold Bluff and Humboldt County were included ; 
also from the beaches from San Francisco south to San Luis Obispo, from 
the elevated beach at Aptos on Monterey Bay, and from the beach at 
Ocean Park near Los Angeles. A report on this investigation was pub- 
lished by Day and Richards^ The investigation included methods of 
separating gold and platinum, and the point is brought out that separa- 
tion is easily accomplished on sized sand with shaking tables of the Wil- 
fiey or similar makes. The sizing is done in a hydraulic classifier or with 
screens. Magnetic separation was investigated also. 

Following is a summary of results from about 200 samples collected 
in California in pounds per ton. Each figure represents the largest 
amount in any sample. 

Maximum found in 
lbs. per ton 

Magnetite 1856 

Chromite 1800 

Ilmenite 1500 

Garnet 1874 

Hematite 1120 

Olivine 836 

Monazite 56 

Limonite 552 

Zircon 928 

Quartz 2000 

Unclassified (in one case largely pyrite) 2000 

"Unclassified" includes grains containing more than one mineral. 

Thus we see that a black sand may be entirely quartz or it may be 
nearly pure magnetite, chromite, or garnet, or it may be 75 percent ilmen- 
ite. Various combinations of the minerals mentioned above and others 
(rutile) are possible. Gold and platinum are often present. The sands 
from various localities have a wide range in composition. 

Many persons have expressed an interest in separating the minerals 
mentioned in the above table and placing them on the market as indi- 
vidual minerals. As no commercial process has yet been dervised by 
means of which this can be accomplished at a profit, attention will be 
given here only to separating gold and platinum from the sand. The 
amount of gold and platinum in the sand is determined by standard 
methods of assaying and chemical analysis. Claims of secret processes 
either for assaying the sand or for recovering the gold and platinum 
should be regarded with suspicion. 

The platinum is usually so small in amount that elaborate machinery 
for its recovery is not justified because of excessive co.st. The expendi- 

1 Day, D. T., and Richards, R. H,, Useful minerals in the black sands of the Pacific 
slope, U. S. Geol. Survey, Mineral Resources U. S., 1905, pp. 1175-1258, 1906. 

(77) 



•LACKK MINING FOR GOLD IN CALIFORNIA I Bull. 135 



r 



..#^'''"-'*^. 



I 








Vir,. :!(i. lii-acli-sancl being: worked witli (lii>-linx, iKjrttu-rii Humboldt ("oiiiity. 
Hvininted from Cdlifornxa Journal of Mines and Geoloffy, October 191,1, p. 50!,. 



Sec. I] TRKATMKNT OF HLACK SAND 79 

ture of $5000 for luacliiiuM-y that would ultimately recover only $1000 
worth of platinum is uuAvise to say the least. Many persons who have 
attempted to recover platinum from the beaches in Del Norte and Hum- 
boldt Counties have failed to realize this. At times the action of the 
waves concentrates jrold and platinum in small areas of the beaches, and 
men are able to make good wages searching for these small patches of 
concentrate and working them by snuUI-scale methods such as long toms. 
Many attempts have been made to work them with machinery but all 
have failed because the deposits are too small to pay for the machinery. 

A similar condition applies to black sand from placer mining. Only 
the large dredging companies have enougli of it to justify the expense of 
much equipment. A dragline dredge is not likely to recover enough 
black sand, but .sevei-al of them together will produce enough to justify 
a little e(iuipment for treatment. Several profitable businesses were 
operated in 1040 by men who collected black sand from a number of drag- 
line dredges and hauled the sand to small plants cfiuipped with amalga- 
mation barrel, small shaking table of the Wiltley or similar type, and a 
melting furnace. The eoncentrate often contains lead shot and bullets, 
which amalgamate. Enough gold sticks to the amalgam and lead to 
make refining in the furnace worth while. A little cyanide or lye is often 
used in the amalgamation barrel to clean tarnished or coated gold. 

Recent practice of two large dredging companies in handling black 
sand is described below. Eai-lier methods are described in a report by 
C. McK. Laizure.' 

One dredging c(mipany reduces the bulk of the sand removed from 
the riffles on the dredge-tables during clean-up to a volume of 90 cubic 
feet with a long tom on the dredge. This amount is sacked and trans- 
ported to a clean-up room ashore. It is ground in an amalgamation 
barrel in which several flat weights are placed to polish the gold, then 
discharged to a sluice and run over a pool of (piicksilver. A bafitie is 
l)Iaced above this pool of (juick.silver so that particles of gold will be 
forced downward against the quicksilver. The mixture of sand and 
water then flows over a copper plate treated Avitli (piicksilver to amalga- 
mate gold. KifHes in a sluice 1 foot wide below the plate recover plat- 
inum in about 100 pounds of sand. This is panned down by hand for 
final recovery of platinum. 

Another dredging company accumulates larger (piaiitities of black 
sand and has a more elaborate plant ashore. Black sand is dumped into 
a bin from which a bucket-elevator rai.ses it to a small ]iulsator jig.' One 
of the functions of this jig is to remove tramp iron and other .scrap metal. 
About two buckets are filled per day from the hutch and this is worked 
down by hand for tarnished or coated gold and platinum. Overflow 
from the jig goes to a Straub^ rib-cone ball-mill then to a shaking copper 
})late treated with quicksilver for amalgamation, then to ii hydraulic cone. 
Some (luicksilver and a little amalgam are recovered in the underflow 
from this cone, but practically nothing else. This underflow is hand- 

= Laizure C McK., Elementary placer mining; in California and notes on the 
milling of gold' ores : California Jour. Mines and Geology, vol. 30, pp. 228-233, 1934. 

:' Pan-American Kngineerlng Company, 820 I'arker Street, Berkeley, California, 

< Made by Straub Manufacturing Company, .")07 Chestnut Street, Oakland, Cali- 
fornia. 



80 l'LA(i:U MININ(i I'OK GOI.D IN' CAT,1K0RNIA |r>u]1.13r) 

worked. The overflow poes by pipe-line to a Wilfiey table 4^ by 8 feet. 
Concentrate from this table goes to a Wilfiey table of laboratory size, 
IJ by :i feet, roncentrate from the small table is hand-panned; mid- 
dliii'T is returned to the same table. Tailin*,' from the small table and 
middlin},' from the lar<re table t^o back to the ball-mill. Tailing from the 
large table goes to a hydranlic cone, from which the overflow goes to 
wa.ste. Underflow goes back through the entire plant. 

If the three products that are hand-worked contain nnich rusty gold, 
they are treated in a second small ball-mill in batches for polishing. 
Amalgam is sometimes treated in a pebble-mill made of a 3-gallon stone- 
ware crock containing flint pebbles. This tends to free much of the 
platinum tliat may be entrained in the amalgam. 



DRIFT MINING 
GENERAL DESCRIPTION* 

Drift mining in the United States has been applied chiefly to the 
exploitation of buried Tertiary river channels in the foothills of the Sierra 
Nevada in California. It has also been applied extensively, although on 
a smaller scale, to the mining of rich streaks on or near bedrock in more 
recent gravels where pay dirt is covered with a thick mantle of unpro- 
ductive material. Ground may also be drifted where there is insufficient 
p:rade or water for hydraulicking or where conditions are unsatisfactory 
for dredging. Bedrock under rivers has also been drifted where it was 
impracticable to divert the stream ; however, loose gravel containing a 
large quantity of water cannot be mined successfully by drifting. 
Usually the method is one of last resort and can be applied only to rich 
gravel. Even under favorable conditions 6 feet of gravel on bedrock 
generally must average at least $2.50 per ton to be mined profitably by 
drifting. Ground that has been drifted by the oldtimers with limited 
capital has been worked by other methods later; in these instances the 
overburden carried enough gold to pay for mining on a large scale. 

In the latter part of the nineteenth century many large and produc- 
tive drift mines were operated in California; according to Hill,^ 11 mil- 
lion dollars in gold was produced in California by this method from 1900 
to 1928, inclusive. In the summer of 1932, however, there were no large- 
scale operations in the United States, and the production of gold by this 
method was relatively unimportant. Two well-equipped properties, 
Vallecito Western and Calaveras Central, were doing development work 
but no regular breasting. ^ The washing plants were used when enough 
gravel had accumulated to run the plant most of a shift. A few men 
were emploA^ed at a number of old properties in an endeavor to find new 
deposits of gravel. At a few other old mines lessees were taking out a 
very limited tonnage from around old workings. Throughout the west- 
ern placer districts small operations were under way, but relatively little 
systematic breasting was being done. 

Most of the present drift mines are operated through shafts, although 
ill the past some large and productive mines were worked by adits. In 
many districts large quantities of water must be pumped. 

Ill mining, the gravel is either drilled and blasted or picked by hand 
to break it down, then it is shoveled into cars and trammed to the sur- 
face or to the hoisting shaft. At the surface the gravel is sluiced or put 
through a washing plant to recover the gold. The gravel from most drift 
mines requires mechanical methods of washing to disintegrate it and free 
the gold. 

Milling practices bear no direct relation to mining methods at drift 
mines and are treated separately in this paper. 



» The following general description of drift mining consists of extracts from 
Placer mining in the western United States, Part III, Dredging and other forms of 
mechanical handling of gravel, and drift mining, U. S. Bur. Mines Inf. Circ. 6788, 81 
pp., 1935, by E. D. Gardner and C. H. John.son. 

Additional details on methods of drift mmmg and methods of washing the gravel 
for recovery of gold are contained in this bulletin in Section IV, In which individual 
mine.s are listed by countv and described. See Calaveras Central, Calaveras County; 
Ruby mine, Sierra County ; and Vallecito-Western, Calaveras County. 

1 Hill, J. M., Historical summary of gold, silver, copper, lead, and zinc produced 
in California, 1848-1926: U. S. Bur. Mines Econ. Paper 3, 22 pp., 1929. 

^ 2 "Breasting" is the term used in drift mining to designate the mining of the 

gravel ; it corresponds to "sloping" as used in lode mining. 

(81) 



82 I'LACER MINING FOR OOLD IN CALIFORNIA [Bull. 135 

Development 
General Development 

TIk' j,'(MU'ral development plan of a drift mine usually resembles that 
(.f a lode mine ^vlleI•e similar Hat-lying deposits are exploited. Lateral 
development and the blocking out of the pay gravel are modified to fit 
local conditions. 

Bench deposits or old channels exposed by later erosion or covered 
by only moderate deptlis of overburden may be opened and mined 
throufrh adits. Ventilation shafts, however, may be required in exten- 
sive workin<,'s. 

Deeply buried deposits must, of course, be mined through shafts. 
This form of entry also is used for mining relatively shallow deposits 
wliere adits are not practicable. Occasionally long drain tunnels will be 
run and the gravel mined thnmgh a series of shafts sunk along the course 
of the pay gravel. I\Ioreover, shafts may prove more economical for 
mining shallow deposits where their use obviates long underground trams. 
Conversely, adits may be run for drainage and to work gravels which 
have been developed through shafts. 

Some of the ancient channels are buried as mucli as 500 feet deep by 
later gravel and lava Hows or beds of volcanic ash. The gravel is hoisted 
through a central shaft ; one or more auxiliary shafts usually are required 
for ventilation. A buried gravel deposit generally is prospected by a 
drift along the course of the channel and crosscuts from the drift to either 
lim. Kaises also are occasionally put up to prospect for possible rich 
strata above. As stated elsewhere, the buried Tertiary channels of the 
Sierra Nevada are not related to tlie present stream system; competent 
geological advice is needed to plot their probable course and aid in their 
development. 

Adits sliould be run at such a horizon or .shafts sunk deep enough 
to insure di'ainage in the Avorkings. Drifts generally are run upstream to 
allow drainage to the shaft or out of the entrance adit. Where water is 
not a serious item drifts may be run both ways from a crosscut or a shaft; 
any water from the downstream branch is pumi)ed into the drainage sys- 
tem. The brea.sting is done upgrade by retreating toward the shaft or 
cro.sscut. At drift mines in the frozen gravels of Alaska the common 
practice is to drift in both directions from a shaft. 

Ideal conditions, of course, would be an even bedrock and a grade 
sufficient to allow drainage but not too steep for easy tramming; such 
conditions, however, .seldom exist. A prospecting drift may be run 
partly in bedrock to avoid swinging it from trough to rim and back again 
.so as to keep a practical grade for tramming. With a rapid rise of bed- 
rock, h<»wever, as where a waterfall or rai)ids existed in the original 
stream, the drift has to be run entii-ely in bedrock with raises put up to 
prospect the gravel above or the drift continued on a higher level with a 
transfer point at the break. This, of course, increases the cost of han- 
dling the material. If the size of the deposit as shown by the develop- 
ment work justifies the initial expense, tramming drifts may be run on 
an even grade in bedrock and the gravel from breasting operations above 
dropi)ed into raises from which it can be drawn into cars. Then the 
development drifts and crosscuts are used for extracting the gravel. 

Sometimes drifts at different levels are run from the shafts to mine 
deposits at these horizons. More than one channel may be worked from 
the .same .shaft. 



See. I] DRIFT MINING 83 

In sliallow deposits little or no meclianical equipment may be used 
except for hoistinj;; in small-seale work lioistinf? also may he done by 
liand. The development and mininjr of deeply buried channels require 
expensive installations and usually must be done on a moderately large 
scale. Iloistins' and pumpiufr equipment and air compressors such as 
those used for lode mininjr are re(iuired for mininp: this type of deposit, as 
well as air drills and mechanical haulage equipment. 

Shafts. Siiafts seldom have over three compartments; in small- 
scale Avork one compartment usually suffices. Untimbered shallow shafts 
may be as small as 2 by 5 feet, the minimum section in which a man 
can dig. 

Sinking practices are similar to those at lode mines except that blast- 
ing is seldom done; the gravel is loosened by picking or moiling. The 
shaft lining asually consists of lagging back of standard framed-timber 
sets.* 

Considerable water may have to be handled in sinking deep shafts 
in gravel, in which case ample pumping capacity is needed. Ordinary 
sinking pumps usually are employed. Steffa * has described the sinking 
of a 2-compartment shaft at Vallecito. California, in which a novel method 
of handling the water was used ; other sinking practices at this mine, how- 
ever, conformed to the general practice. He states : 

'•The shaft of the Vallecito Western was located at a point 50 feet north of the 
actual channel in order that the shaft station, at a depth of 153 feet below the collar, 
niifcht he in the solid .slate bedrock. At the point selected the shaft passed through 
14.3 feet of volcanic cobl)le, ash, and sand and gravel before reaching the slate. It was 
sunk a total depth of KiT feet, providing a 14-foot sump below the station. 

"The shaft is 4 feet by 7i feet in the clear and has one 4- by 4i-foot skip com- 
partment and a 2^- by 4-foot manway. It is timbered with 8- by 8-inch Douglas fir, 
excepting that 6- by 8-inch material was used for dividers, and is lined with 1- by 
12-inch boards. 

"The shaft was sunk to Itedrock without blasting, picks and gads being sufficient 
to loosen the material for .shoveling. The 24 feet through rock was sunk by hand 
drilling, using 10 to 12 holes per round, light charges of powder, and electric delay 
detonators. 

"A 12-inch churn-drill hole was sunk first at one end of the shaft to handle the 
flow of water which was struck at a depth of 8 feet and amounted to about 3.j gallons 
per minute throughout the work. The hole was sunk to a depth of 187 feet and cased 
with perforated 7-inch in.sjde diameter stove-pipe casing. A deep-well type of turbine 
pump was installed which was powered with a 20-hp. vertical electric motor, the motor 
resting on staging about 4 feet above the shaft collar. Three-foot lengths of pump 
column were used, and as the shaft deepened from day to day enough blocking waa 
removed from under the motor support to keep the pump intake at the level of the 
i)ottom of the shaft. When blasting, during the latter part of the work, the casing 
and punip column. exi)osed in one end of the shaft, were protected from damage bv a 
heavy plank hung from the bottom end plate directly in front of the drill hole. 

"Xumerous strata of sand and volcanic ash were encountered, one such bed at 
a depth of 70 feet being 7 feet thick. A large part of this fine material was carried 
to the surface by the pump. A test showed that at one time the pump discharge was 
one-third sand by volume. The pump Impellers wore rapidly, three sets being used. 
Moreover, the drill hole rapidly filled with .sand to the level of th«> pump, after which 
the pump could not be lowered farther. Twice the pumj) was removed and the h(de 
cleaned with a sand pump. Finally, at a depth of 75 feet, this difficulty was remedied 
by cutting a slot in the casing of the hole, wide enough to in.sert a hand to clean out 
the sand. As tiie shaft deepened the .slot was likewise cut down. To .secure suction 
with a shallow sump, such as could i)e dug out easily by hand in this manner, a 4-inch 
strainer was substituted for the original 3-foot one. The pump was run continuously 

3 Gardner, E. D.. and John.son, J. F., Shaft-sinking practices and costs- tt «5 
Bur. Mines Bull. 357, pp. 4S-G0, 1932. cosis . u. fa. 

* Steffa, Don, Gold mining and milling methods and costs at the Vallecito Westprn 
drift mine, Angels Camp, Calif. : U. S. Bur. Mines Inf. Giro. 6612, p. 7, 1932. ^••'='n 



.S4 



PLAfKR MININC I'OR (UHA) IN CALIFORNIA [Rllll.l.Sr) 




VERTICAL SECTION 





1 




6-inch I beam 


^ 


ganger 




■z^ 


— 







t== 


J""" 


r"" 


iJ 










' 1 












b 

In 


b 

X 

o 




U- 
(he 


HANGER 
•vy sttel) 












" 


1 " H 


6-inch I beam 




jcHanger 










= = 


1, = = .. 


H 










r 




Lj 







I 1 

I I 
I J 



PLAN 

Fio. 31. Method of spiling in loose ground. 



♦2- 



Sec. I] DRIFT MINING 85 

and regulated by the gate valve on the discharge pipe to the exact amount of water 
flowing into the small sump. 

"It required 00 days to complete the siiaft. The average progress in sinking, 
including timbering, was slightly less than 1 foot per shift, working two 8-hour shifts 
per day. The cost was $39.50 per foot. Shaftmen and the foreman received $6 per 
day and engineers $5. Timber and lumber laid down at the shaft cost $42 per thousand 
board-feet." 

Drifts and Crosscuts. As used in this paper, a "drift" designates 
a development working- parallel to the major axis of the deposit ; a " cross- 
cut" is a transverse working. This distinction is not observed strictly 
in the terminology of the mining districts. 

Drifts may be run as small as 3^ by 5i feet in section where the han- 
dling of a minimum of material is desirable. In pay dirt they may be 
run up to 7 by 9 feet in size or as large as they can safely be held. The 
size of crosscuts depends upon the service required of them. 

The gravel in the ancient channels generally is compact enough to 
stand Avithout timbering; blasting usually is required. The number of 
holes required to the round depends upon the compactness of the gravel. 
A simple toe-cut round — that is, one with the cut holes pointing down- 
ward — usually suffices for breaking the ground. It is desirable when 
blasting pay dirt in both development work and breasting to pulverize it 
as much as possible to facilitate washing operations. Ileavy blasting, 
however, should be avoided so as not to scatter the gold-bearing gravel. 
In loose gravels the main difficulty in driving may be to prevent caves 
until the timbering is in place; the gravel is excavated by picks and 
shovels. 

Wheelbarrows may be used in short drifts or buckets on trucks in 
small-scale work where the broken material is hoisted. In more elaborate 
workings, however, cars running on rails are employed. 

For drifting in pay dirt, a wide drift may be run and the boulders 
piled at the side to form dry walls. Where timber is brought from a dis- 
tance regular drift sets of square timber generally are used for support- 
ing the drifts, but if round timber is available locally sets usually are 
made of it. The posts of the sets generally are stood with a batter so that 
the drift may be given a section more nearly approaching an arch. 

In loose or running ground spiling or forepoling must be used. The 
first step in spiling is to place bridging over the foremost standing set. 
Bridging u.sually consists of a 4- by 8- or 4- by 10-inch lagging laid par- 
allel to the cap on top of 6-inch blocks at either end. This lagging is 
blocked solidly to the ground above, leaving a space 6 inches high above 
the cap through which the spiling is driven. If side spiling is necessary 
bridging is placed on the outside of the posts. Spiling usually consists 
of 2- to 5-inch timber 4 to 10 inches Avide and as much as 9^ feet long, 
depending upon the weight to be borne and ease of driving ; one end of 
the spiling is sawed on a sharp bevel. The top spiling is driven at an 
upward angle into the caved or loose ground. In mines having com- 
pressed air a drilling machine with a special tool may be used for driving 
the spiling. The spiling extends over the cap far enough to provide room 
for placing a complete set. The upward angle is sufficient to allow bridg- 
ing to be placed over the new set. The first spiling usually is driven at 
one side of the bridging close to the bridging block at such an angle that 
the forward end when in place will be 6 or 8 inches beyond and above the 
cap and close to the wall. The remaining ones are driven at such angles 



86 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

that they "fan" and form a complete covering for the set of timber to 
be pnt in place. As each spiling is driven ahead some of the gravel i3 
cleared away from nnderneath it so that if any large boulders are encoun- 
tered ahead of the spiling they can be barred out of the way or taken 
down. After the top spiling is in place side spiling, if necessary, is 
driven in the same manner, beginning at the top. Two 6-inch I-beams, 
or heavy timbers, are then hooked on tlie la.st cap by heavy steel hangers. 
The ends of these beams are extended forward to just back of where the 
cap of the ne.xt set will be when in position. A crosspiece is then placed 
across their forward ends and brought up snugly against the spiling; the 
back ends of the beams are blocked down under the second cap back. 
"When the gravel is removed the next set is put in. The beams support 
the top spiling while the set is placed. Posts and caps of ordinary drift 
sets are used. 

The same method of top spiling is used for breasting in running 
ground. The I-beams or timbers with overhead lagging may be used in 
firmer ground to protect men working ahead of the last set in position 
from falling material, both in drifting and breasting operations. 

.Steffa •* gives the drifting practice at the Vallecito drift mine as 
follows : 

"Both f,'iin>,'Wii.v.s and crosscuts are generally 7 by 7 feet in sectiou. The usual 
(hill riiimd consists of six holes drilled ."> or (> feet deep and lireakiiiK an average of 
4 feet per round. The gravel drills easily, 2i hours generally being sufficient to drill 
the roun<l. Drill steel is of |-inch hollow-hexagonal material, sharpened with cross 
bits. Slightly nii>r»' than !• jiounds of '2'> percent strength i>owdf»r is used per round, 
with four sticks in each of three lifters, three sticks each in the two cut holes, and two 
in the single back hole. Caps are treated with a standard waterproofing compound. 

"The broken gravel is shoveled by hand into IS-cu. ft. end-dump, roller-bearing 
cars holding 1 ton each. Track consists of IG-pound rails laid to IS-inch gage. The 
grade of the channel has proved uniform over considerable distances and averages 
75 feet to the mile. Track has been laid therefore on a grade of 1^1 percent upstream. 
It has seldom been necessary to take up bedrock to maintain the grade ; wherever a 
dip in the floor has Iteen f<iund the track has been kept on grade, and bedrock has 
always been found at the expected elevation when reaching the oi)posite side of the dip. 

"In the opening of new areas by drifts or crosscuts, .samples are taken from the 
skip at the collar of the shaft, a .sample consisting of one full pan or about 20 pounds 
of gravel. Samples taken at this point have the advantage, as compared with samples 
taken from the .solid face, of being representative of a larger volume of ground and of 
being mixed thoroughly by the blasting and by the handling of the gravel from muck 
pile to car and to skip. Thus an experienced paiiner is able to make fairly accurate 
estimates of the value of the gravel developed. 

"Drifts and crosscuts are driven by crews of three or sometimes four men, making 
an average a<lvaiice .»f 4 feet per shift. The cost of driving main headings averages 
*H> to $17 per foot. In a pay area (5.j feet wide, where gravel can be breasted 10 feet 
high, eiich foot of heading developinl 4."» tons of gravel. (It is estimated that the gravel 
ex|>ands one (piarfer on being broken, and a ton of broken gravel has a volume of 
l« cubic feet.)" 

The cost of running a drift under average conditions at a small-scale 
ninie where no other work was being done was shown by the Golden Belt 
(iold Mining Company which was developing a drift mine on Magpie 
(iidch near Helena. Montana, in the summer of lU'.Vl. An 80-foot shaft 
had been sunk, and a drift was being run up the channel ; the drift was 
160 feet long and 5 by 6 feet in section and was timbered with 8-inch 
round timber .sets placed 4 feet apart. The top and sides of the drift 
were hned with split lagging. The timber was cut and sawed on the 
t?''"""d. The gravel was picked by liand and trammed in a 6-cu. ft. car. 

drift mlnt^^A.^^^ 9''^^^ "^1^'?? *"<J ""'"J"^ methods and costs at the Vallecito Western 
drift mine. Angels Camp. Calif.: U. S. Bur. Mines Inf. Circ. 6612, pp. 8-9. 1932. 



See. I] DRIFT MINING 87 

It was hoisted in the body of the car, which at the surface was placed on 
a truck and trammed to the washing plant. The cost of running the 
drift was $6 per foot, excluding supervision. The surface equipment 
at the shaft consisted of a headframe and a hoist run by a 15-hp. electric 
motor. Power cost 1.07 cents per kilowatt-hour. 

An example of the cost of running a drift under adverse conditions 
in small-scale operations was illustrated at the Lucky Charles Mining 
& Milling Company small drift mine on North Clear Creek, Blackhawk, 
Colorado, which in July 1932 was being developed through a 40-foot 
2-compartment shaft ; 50 feet of drift had been run but no breasting done. 
The property was well equipped with an electric hoist, a deep-well pump, 
a substantial headframe, and an ore bin. About 20 gallons of water was 
being pumped per minute. A 10-hp. motor operated both the pump and 
a hoist which had an 18-inch drum. The gravel was hoisted in a 7-cu. ft. 
bucket attached to a ^-inch cable. 

The gravel was 3 to 5 feet thick and was overlain with 5 feet of quick- 
sand which required both top and side spiling. The drift was 6 feet 
high, 5 feet wide at the top, and 6 feet wide at the bottom. Sets of 6-inch 
round timber were placed 2 feet apart. Top spiling was 3 by 6 inches by 
5^ feet ; side spiling was 1-inch boards. 

An advance of 1 foot per day was being made by 2 men underground 
and 1 man on the surface. The cost per foot of drifting was as follows : 

Labor (3 men at $4) $12.00 

Power (hoisting) 1.00 

Timber 1.80 

Other supplies 1.00 

Total $15.80 

Breasting 

A number of different methods of breasting are employed at drift 
mines, depending mainly upon the nature of the deposit. Drift-mining 
methods were evolved in the early Californian diggings ; present methods 
do not differ materially from those of the early days. 

In narrow channels the gravel may be mined on either side of the 
drift as it is advanced or the drift advanced the full width of the pay 
streak. In wader deposits the drift may first be run to the limit of the 
deposit and then the gravel mined, retreating toward the shaft. In exten- 
sive deposits the gravel usually is divided into blocks preparatory to min- 
ing. The blocks generally are mined by retreating. Pillars usually are 
employed only to protect haulageways. A modified room-and-pillar sys- 
tem, however, has been used at some mines in which the pillars, if in rich 
gravel, were later ren^oved. 

Breasting may be done from crosscuts or from drifts run parallel 
to the haulageway. Breasting from the crosscuts may parallel the haul- 
age drift on the retreat toward it. When working from drifts the line of 
retreat usually is parallel to the drift although sometimes toward it. The 
spacing of crosscuts or drifts at different places ranges from 40 to 200 
feet, depending mainly on the sy.stem of breasting. Crosscuts generally 
are turned off at such an angle as to give the proi)er gradient for tram- 
ming. 

Cuts or slices range from 2^ to 8 feet wide. If cars are used in long 
faces the tracks are shifted after each cut. Usually all of the gravel 
rich enough to mine and enough of the overlying gravel to provide head- 



88 PLACER MINING FOR GOLD IN CALIFORNIA [Bllll. 1M5 

room is taken out. Rooms generally are 6 or 7 feet high ; the minimum 
height in large operations is 5 feet. At the Valleeito mine, described 
later, the thickness of the pay dirt varied up to 14 feet, although at most 
mines it was less than 6 feet. The rooms may be broken to a strong strata 
of ground where such strata occur. In some California drift mines vol- 
canic ash makes a strong roof. 

In compact or cemented ground the breasts are broken by blasting 
drill round ; holes may be 2^ to 6 feet apart. At most places, however, 
breasting is done with picks. At many places the gravel is undercut, 
usually in the upper and softer part of the bedrock ; tiie remaining gravel 
in the face is then broken to the undercut. Usually 1 or 2 feet of bedrock 
is taken up. Often, bedrock with deep crevices containing gold can be 
picked. Hard bedrock is cleaned carefully by hand, as in surface min- 
ing. Boulders and gravel too low in grade to take out are piled back 
of the working face. 

Low-built cars usually are preferred for the sake of easier shoveling 
and tramming in the low workings. Scrapers in drift mines have not 
proved successful, but with the recent improvements in equipment and 
technique this method of moving gravel offers possibilities. 

Some timbering usually is required in breasting, if only an occasional 
stuU which may be recovered later. Regular timbering consisting of 
stulls with headboards is used at most mines. If the bedrock is soft, foot- 
boards also are used ; in soft ground lagging is required overhead. Heavy 
ground generally is supported by lines of sets. In narrow channels 
tunnel sets with long caps may be used. 



A SYNOPTIC PRESUMPTION 
REGARDING CALIFORNIA'S DRIFT MINES 

By L. L. Huelsdonk* 

In years past, including but not considering the war and closing 
order L-208 of the War Production Board, there have been many theories 
advanced, from the rapid extinction of the old-time gravel miner and the 
inability of the present generation to absorb his art to the exhaustion of 
the ancient river channels, for the sick condition of the California-sired 
and once booming drift mines. The actual reason is without doubt 
economic, and depletion of the easily accessible channels is probably the 
chief contributing factor. However nearly all of the successful drift 
mines operated at a time prior to the epoch of laws, rules, regulations, 
restrictions and taxes governing compensation, unemployment, social 
security, sales, income, corporation, labor, forest, water, transportation, 
tailings, and many other seemingly unimportant riders regulated under 
some admixture of the ABC's which directly or indirectly affect present- 
day operations. 

In the so-called 'good old days' a drift miner often wore knee-pads, 
worked long hours under a goose-cooker, back-filled boulders and waste 
and loaded only select pay dirt into his breast buggy. This was trans- 
ferred to cars and trammed to the outside washing bins by Chinese labor 
where even in the larger mines, the superintendent had the time and did 
in most cases wash the gravel and make the clean-up, He fed the white 
miners beans and the Chinese rice, and if after meeting the payroll and 
bills an ounce of gold remained the mine was a profitable one. He 
needed no accountant, income tax expert, attorney or engineer to esti- 
mate ore reserves, values, percentages of depletion or other incompre- 
hensible guesses to determine if the profit w^as actual or merely one on 
paper. 

The foregoing is not an advocation for the return of the * good old 
days' Qr is it without exaggeration or exceptions. Its main intent is to 
express in brief generalities, for comparable purposes and the sake of 
argument, conditions that existed during California's early-day drift 
mining history. As a conservative estimate these mines had an over-all 
cost of possibly $3.50 to $4.00 per man-day as compared to an immediate 
pre-war average of $10.00 and a probable $15.00 post-war outlook. This 
means simply that on the basis of a 50-man crew the early day operation 
had a monthly cost of approximately $5600.00 as against $15,000 in the 
late 1930 's and $22,500 for crystal ball operations. So in order to keep 
the unit cost of gravel washed on an equal basis it will without much 
doubt be necessary for the post-war operator to wash four times the num- 
ber of units per man as did the old timer and one and one-half times as 
many as those washed just prior to the war. In comparing these (exclud- 
ing tax and other ABC nuisances which have been included in the man- 
day costs) many other factors must be considered, such as the highly 
publicized $35.00 gold and the possibility of a future increase, the amount 
of waste mined with pay, the efficiency of up-to-date equipment and 

• Superintendent, Ruby mine, Downieville, California. Mr. Huelsdonk explains 
in a letter that these remarks apply to drift mining in general and that exceptions exist, 
such as the Ruby, where rich beds of coarse gold are found ; but that these have little 
bearing on the industry as a whole. 

(89) 



DO PLACKR MININC VOH COlAy IX CALIFORNIA [Bllll. 135 

lUJU-hituM-y, workiii;,' liours, iiiodeni explosives, high-«?rade control, gold 
recovery, niaiiapeineiit and eiiprineeriiig facilities. Since most of these 
are incidental we will consider only the first {rronp, that is $35.00 pold, 
its possihle increase, the efficiency of modern eqnipment and the ratio of 
waste to pay mined. The old timer mined very little waste, he worked 
by hand, tlie {gravel was prospected, he .skipped the ]K)or, mined the pood, 
and at times took only a few inches of bedrock <xravel by back-filling 
waste and Icaviiif; jnst enonph room to work. Even if the post-war man 
wonld snbniit to this type of mining the over-all cost per miner would 
without doubt be j)roiiibitivc and therefore any post-war drift mine 
plans nnist include the use of modei-n eciuipment if success is to be reas- 
niiably expected. However, this is not an over-all answer or is it without 
drawbacks. What we might consider modern drift mining equipment 
are<nncking machines and slusher scrapers supported by various acces- 
sories such as power augers, jack legs, air bars, drifters, electric loco- 
motives, etc. To begin with, even the smallest mucking machine requires 
a seven-foot high face to woi-k in and if in a timbered drift, eight feet. It 
reipiires a track, and grade must be maintained. Tts operation cannot 
be held up while boulders are sorted out and back-filled, as its prime pur- 
pose is a muck moxci- and any delays must be ))roi)()rtionately charged to 
costs. Also since the bulk of the gold lies on the bedrock or a few inches 
above it in mo.st drift mines, breasting with a mucking machine usually 
causes undue dilution. Tts use, however, is indispensable around the 
modern drift mine for running bedrock tuiniels and where applicable for 
opening up grouiul for slushing. 

liy breasting with .slushers a fairly nu)dcrate roof heiglit can be 
maintained. This must, however, be at least five feet in order to make 
working roojn and conform substantially to modern working conditions. 
P>y usi)ig blasting boards to keeji from scattering the ])ay over the worked- 
out areas and at the .same time utilizing them for a scrajier way during 
the nuicking cycle a good condition is civated for back-filling boulders 
in the open breast. Heavy rocks can be pulled over the boards by use o£ 
the tu<rger and a duiin net sling. A scraper also has the advantage of 
following over irregular bedrock (when the gravel is reasonably dry) 
without grade or drainage. It is also a good bedrock cleaner when 
l)roperly applied. In other words, the slusher, under ideal conditions 
is a hard combination to beat for brea.sting purposes. It is not however, 
without faults and disadvantages. The scrapers have a tendancy to cut 
and follow troughs in the broken gravel making it hard to crowd the face 
and mechanically clean uj) the breast for drilling. In wet ground they 
stir and mud the gravel making a .sticky nui.ss which is very difficult to 
handle in the chutes, cars aiul ore bins. Tender these conditions they 
sometimes bury themselves and <'Ut deep into the softer bedrock spots 
forming i)\Kldle holes wliich catch more water and tend to further wet 
the nnick. Also selective breasting cainu)t be carried on .successfully as 
the main theme nuist be the .si)ii-it of high production and low costs and 
therefore the drilling and mucking cycles cannot be interrupted. In 
((thcr woi-ds with a hundred-foot breast face with fifty feet averaging 
$fi.00 and fifty feet averaging 10 cents the entire leiigth'must necessarily 
be taken rather than rearrange set-ups to take .select sections. This 
further tends to dilute; the pay when comparing it to the old-timer's work. 
Also tugger stations contribute waste and their setups absorb man power. 



Sec. I] CAI.IFOUNIA's DKIFT MINKS — TU'EI-SDONK 01 

In suuiniiiig these groups we might say tliat iiiodeni breasting, no 
matter how closely guarded, will add an equal amount of waste to the 
pay gravel mined by the old-timer, so therefore, although the present 
price of gold is $35.00 per ounce it lias a modern drift mine value of only 
$17.50 as compared with .$20.67 for the old-timer. Consider with this the 
four to one mining ratio anticipated for post-war operations and the gold 
for this operator will have a value of less than $5.00 per ounce on a com- 
parable basis. In other Avords, to balance the two periods, the post- 
war drift mine operator should get $41.34 per ounce for his gold to com- 
pensate for dilution necessary with modern methods, and since he will 
be required to wash four times the amount of diluted pay dirt to obtain 
an equal unit cost he should receive a total of $165.36 per ounce for his 
gold to reach the boom basis of the drift miner's heyday. 

These figures, although subject to considerable variation, will serve 
in a general way to explain the sick condition of California's drift mines. 
Providing that gold remains at its present value or enjoys an increase 
with a compensating sur-tax the post-war drift mine operator, in order 
to effect a cure, must be a strong-minded, hard-headed doctor willing to 
suffer public criticism by experimenting with and practicing ultra- 
modern methods such as tlie rapid back-filling and tamping of w^aste into 
the 'worked-out' areas by specially designed machines that will insure 
safe working conditions aud eliminate to a great degree one of the indus- 
try's main bugaboos, the expense of timbering. He will have to work 
out a ratio between the expansion of his broken ground and the tightness 
of his back-fill whereby he will be able to haul out and wash only his 
richer bedrock gravel and thus minimize transportation and milling costs. 
His development program miLst be carefully laid out and his plans must 
include the mining of the entire bedrock area as there can be no applied 
rule for following the pay .streak in this type of mining and as some gold 
usually spreads over the bedrock aside from the run of gold the effort 
would in most cases be compensated for hy low mining costs. 

The small amount of gold accompanying the upper gravels which 
w^ould go into the back-fill would no doubt be cheap pay for the fill 
material. 

In conclusion, it might be generally .said that if gold remains on a 
par with its present value and if the po.st-war drift miner is to enjoy the 
higher (or any) income tax brackets, he must develop and adopt a more 
streamlined mining system rather than knock his brains out against Davy 
Jones' locker with the present day conventional methods. 



02 



PLACKR MINIXt; I'OK GOLD IN CALIFORNIA [Bull. 135 












Fig. 32. Flume for hyflraulic mine under con.><trutti(in. Pliolo by C. V. Avcrill. 



HYDRAULIC MINING* 
i. . Application 

; Jn hydrf^ulic niininp: a jet of water issuiiif]: under high pressure from 
a nozzle excavates and uaslies the gravel. The gold is recovered partly 
by^,cleaiiing bedrock after the gravel has been .stripped away but chiefly 
by riffles in the sluice box through which the washed gravels and water 
flow to the tailing dump. 

Almost all types of placer deposits can be worked by hydraulicking 
if water is available but certain physical characteristics have an impor- 
tant bearing on the cost of the operation. If the gravel is clayey, the 
washing is more diffieuJt but more important. If the gravel is cemented, 
it can be cut only by high-pressure water. If the grade of bedrock is 
flat, the duty (cubic yards per miner's inch or other unit) of the water 
is relatively low, and where gravity disposal of water and tailings is 
impossible or impracticable elevators must be used to raise them from the 
pit, further decreasing the capacity of the installation. 

Apart from the deposit itself, the water supply is the most important 
factor in determining the application of hydraulicking and the scale of 
operation. Under any given conditions, the daily yardage is roughly 
proportional to the quantity of water used. The quantity excavated 
likewise is proportional to the head used on the giants, but the higher 
pressure is of less value in driving and washing and of none at all in 
sluicing the gravel through the boxes to the dump. As the cutting and 
sweeping capacity of the giants usually exceeds the carrying capacity of 
water a stream of flowing water, known as "by -wash", or "bank water", 
is directed through the pit and into the sluices. If run over the bank, as 
in ground sluicing, it aids materially in cutting the gravel. The proper 
relative quantities -of high pressure and bank water can be determined 
only by trial. Frequently the by-wa.sh is supplied by the natural flow of 
the .stream at the mine, the giant water being brought from a considerable 
distance up the stream or from another source. "When an excess of bank 
water is available it may be used for ground-sluicing, thus increasing the 
capacity of the plant. 

The preparatory or development work necessary to start hydraul- 
icking usually is greater than that for any other form of placer mining 
except dredging or drift mining. A deposit preferably is opened at the 
lower end to permit gravity drainage and progressive mining of the entire 
deposit in an orderly fashion. If the gravel is thick or the grade of bed- 
rock flat, a very long cut may be neces.sary to reach bedrock at the desired 
point. This may involve the mining of large quantities of barren or at 
least unprofitable gravel. A more important element of preparatory cost 
is the water supply. As heads of 50 to 300 or 400 feet are desired, a mile 
or more of ditch or flume is almost always necessary to bring water onto 
the property by gravity flow. A single mine may have many miles of 

* The following infoiiiiation on the general subject of hydraulicking consists 
largely of extracts from Placer minUty in the western United States, Part II, Hydraul- 
ickimj, treatment of iihucr concentrates, and viurketiny of ffoUl, U. S. Bur. Mines Inf. 
Circ. 6787, pp. 3-1 US, 1934, by K. D. Gardner and C. H. Johnson. Many of the tables 
contained in that publication have been omitted. Tables showing flow of water in 
pipe-line-s and ditches and over weirs will be found in books on hvdraulics such as 
Hydraulic tables, by G. S. Williams and Allen Hazen, 115 pp., John Wiley & Sons, Inc., 
New York. Gardner and Johnson published tables of prices of pipe and other equip- 
ment, but these have sUiee changed and are likely to change further from time to time. 
Hence such prices should be obtained from manufacturers. 

(93 ) 



94 PLAf:r.R MININT. FOR nOLH IN CAMFORNIA [Rllll. 1^!") 

ditch, costing perhaps $2, ")()() per niilo, as well as dams and resorvoirs and 
thousands of foet of flinnos, tunnols, or inverted siphons. The mechan- 
ieal e(piipinent of a liydraulic mine oi-dinarily consists of a few hnndred 
to a few thousand feet of lO-to :{()-inch, or lar{,'er, iron pipe, one or more 
monitors, and a varyin<: number of sluice boxes; the cost of equii)ment 
ordinarily is small compared to the expenditures necessary for ditches 
and tail races. 

Althonjrh it is obvious that the recoverable gold content of the gravel 
nnist pay a profit over operating costs, which usually range from 5 to 20 
cents per yard, a surprising number of ventures in hydraulicking have 
failed becau.se the promoters have not allowed for all the preparatory 
expen.ses noted above. Each yard of gravel mined must carry its share 
of this cost, therefore the size of the deposit is of utmost importance in 
considering a hydraidic mining venture. 

Hydraulicking under .suitable conditions is a low-cost method as it 
yields a larger production per man-shift than any other method except 
dredging. The initial investment recjuired is less than that for tlredg- 
ing; hence, hydraulicking in small or medium-size deposits may be more 
economical even though dredging would result in a lower operating cost. 
When tiie operations are on a very large scale hydraulicking costs are 
lower than dredging costs on a comparable basis. Very clayey or 
bouldery gravels .should be hydraulicked as dredging usually is unsatis- 
factory in such ground. 

There is enough similarity in all hydraulic operations that no natural 
classifications of the method can be made. The methods of attacking 
the gravel vary too little to make any general distinctions. Factors sucli 
as conditions of the gravel, percentages of boulders and clay, grade of 
bedrock, and quantity and head of the hydraulic water affect the co.sts, 
but no general grouping is possible in accordance with any of these heads. 

Ditches 

Open ditches are used c(mnnonly to bring water close to, yet high 
enough above, the mine to furnish a satisfactory pressure for the giants. 
At several hydraulic mines in the Western States and Alaska ditches 
30 to 40 miles long have been built, and even relatively small operations 
usually have 5 to 10 miles of ditch line. 

Hydraulicking is feasible with heads as low as 40 or 50 feet if the 
gravel is not tight ; however, heads of 80 to 200 feet usually are desired, 
and if the gravel is cemented it is not uncommon to employ high-pressure 
equipment and heads raiiging from 'MK) to 400 feet. This consideration 
fixes tentatively the location of the lower end of the ditch. Its final loca- 
tion may be a matter of compromise, as the head usually can be increased 
only at the cost of a lengthened ditch or a decrease in the grade. The 
latter reduces the quantity of water that can be carried in a ditch of 
given size. 

The grades of most hydraulic-mine ditches lie between 4 and 8 feet 
per mile, or J to 1| feet per 1,000 feet. Early C'alifornian ditches were 
run on much steeper grades, but the conseciuent high velocities caused ero- 
sion of the banks and .serious breaks were common. Small ditches may- 
be run at grades of 6 to 12 feet per mile without excessive velocities. 

Practical velocities range between limits of Avhich the minimum is 
determined by silting and the maximum by erosion. If the entering 
water contains sediment it may be deposited in the ditch. This should 



Sec. I] 



HYDRAULIC MINING 



95 



be {guarded ap:ainst by installing; a sand trap near the intake and by 
designing for a velocity of not less than 1 foot per second. On the other 
hand, a velocity of more than 3 feet per second is apt to erode the channel 
and cause breaks. 

Table 1. Recommended mnaimum mean velocities for ditches in various materials 



Mean velocity 



Material 




Loose sand _. 

Sandy soil 

Loam 

Stiff day, gravel 

Coarse gravel, cobbles 

Conglomerate, cemented gravel, soft rock 
Hard rock 



The figures in table 1 represent mean velocities, the corresponding 
bottom velocities being 20 or 30 percent lower and the corresponding sur- 
face velocities as measured by floating objects possibly being 25 to 35 
percent higher. 

The velocity, hence the capacity of a ditch, depends upon its slope, 
the nature of the walls, the size and shape of the water section, and the 
straightness and regularity of the channel. All these factors, except 
straightness and regularity of cross-section, are involved in the well- 
known Kutter formula : 



1.811 



41.65 + 



0.00281 



1 + 



V 



^(41.. 
R \ 



m -f 



0.00281 



v^ 



in which 

y = mean velocity (in feet per second), 
n = roughne.ss coefficient. 
S — sine of slope (fall divided by lenRtli) . 

R = hydraulic radius (area of water section divided by wetted perimeter of 
channel) in feet. 

The proper values to use for the coefficient w are a matter of judg- 
ment. The values of n reeonmiended by modern designers are shown in 
table 2. 

Earth canals for irrigation usually are designed with n — 0.025 or 
even 0.0225 ; however, the usual hydraulic-mine ditch is not straight, uni- 
form, nor smooth, and probably the coefficient 0.030 or 0.035 should be 
applied. Any increase in the assumed value of n results in an approxi- 
mately equal percentage decrease in the calculated velocity, or a doubled 
percentage increase in the required slope. 

Although the shape of the ditch has a bearing on its capacity, in 
practice the section is influenced more by the method of excavation. 
However, for a giveti area, the section should be so shaped as to have the 
largest hydraulic radius consistent with economical construction. The 
usual earth or gravel ditch for hydraulic mines has a trapezoidal section, 



96 



placp:r mining for oold in California [Bull. 185 

Table 2. Values of roughness coefficient n • 



Surface 



Best 



Good 



Fair 



Bad 



Coated cast-iron pipe 

Commercial wrought-iron pipe: 

Black - 

Galvanized 

Smooth brass and glass pipe 

Smooth hjck-bar and welded "OD" pipe 

Riveted and spiral steel pipe .- 

Vitrified sewer pipe 

Common clay drainage tile 

Concrete pii)e 

Wood-stave pipe 

Plank flumes: 

Planed 

Unplaned 

With battens - 

Concrete-lined channels. 

Cement-rubble surface 

Dry rubble surface 

Semicircular metal flumes: 

Smooth 

Corrugated 

Canals and ditches: 

Earth, straight and uniform 

Rock cuts, smooth and uniform 

Rock cuts, jagged and irregular 

Winding sluggish canals 

Dredged earth channels 

Canals with rough, stony beds; weeds 

on earth banks 

Earth bottom, rubble sides 



.012 

.013 

.009 

.010 

.013 

.010-11 

.011 

.012 

.010 

.010 
.011 
.012 
.012 
.017 
.013 

.011 
.0225 

.017 

.025 

.035 

.0225 

.025 

.025 
.028 



•0.012 

.013 
.014 
.010 
'Oil 
«.015 
•013 
> 012 
,013 
.011 

'012 
'013 
'015 
'014 
.020 
.014 

.012 
.025 

.020 
.030 
.040 
'025 
'0275 

.030 
'030 



'0.013 

.014 
.015 
.011 
'013 
'.017 
.015 
'014 
'015 
.012 

.013 
.014 
.016 
'.016 
.025 
.015 

.013 
.0275 

'.0225 
'.033 
.045 
.0275 
.030 

'.035 
'.033 



0.015 
.017 
.013 



.017 
.017 
.016 
.013 

.014 
.015 



.018 
.030 
.017 

.015 



.025 
.035 



.030 
.033 



.040 
.035 



' Values most used. 

• Part of a more complete list by Horton, R. E., in Eng. News, vol. 75, p. 373, 
1916 ; quoted by Metcalf. L., and Eddy, H. P., in Sewerage and sewage di.spo.sal, 2d ed., 
p. 130, McGraw-Hill Book Company, 1930. 

with a flat bottom 2 to 10 feet wide, sides sloping about 45°, and a water 
depth Oi one-third to three-quarters the bottom width. The sides should 
be excavated at a slope that will be stable in use, otherwise caving will 
result in irregularity of section and consequent less of capacity. The 
side slopes recommended for ditches in various materials are given in 
table 3. 

Wimmler,^ who tabulates data on 35 Alaskan ditches, states that side 
slopes of 45 to 65° are common but that the higher slopes cut down 
quickly. 

On steep hillsides relatively steeper sides and deeper sections may 
be cut if the soil is firm to avoid excessive excavation on the uphill side 
of the ditch. In rock the sides may be vertical; the width should be 
twice the water depth, as in rectangular channels this results in the least 
excavation for a given capacity and slope. Likewise, in rock the size 
may be decreased and the grade increased, thus reducing the yardage of 
rock excavation. Ditches should be designed to run not more than 
three-fourths full, allowing 1 to 3 feet of freeboard. 

' Wlmmler, N. L., Placer-mining methods and costs in Alaska: U. S. Bur. Mines 
Bull. 259, pp. 40-66, 1927. 



HYDRAULIC MININa 
Tahle 3. Side slopes recommended for ditches 



97 





Side slopes 


Material 


Horizontal 
to vertical 


Degrees 




1 : 1 
IH : 1 

2 :l 


45 


Ordinary soil, loose or fine gravel 

Loose, sandy soil 


35 
25 



III porous soil considerable water is lost by seepage. Peele ^ quotes 
Eteheverry as stating that seepage losses range from as little as 0.25 cubic 
foot per square foot of wetted surface per 24 hours in impervious claj' 
loam to 1.0 cubic foot in sandy loam and 2 to 6 cubic feet in gravelly soils. 
It is easily computed that a medium-size ditch, 5 miles long, carrying 
1,000 or 2,000 miner's inches, may lose 5 or 10 percent of the intake 
water by seepage, even in good soil, and in porous soil, as much as 20 
percent. Remedies where the loss is serious are to decrease the size of 
ditch and increase the velocity; to reduce the velocity to a point at which 
the silt will deposit and tend to seal the ground ; to line the channel with 
sod, canvas, or concrete ; or to substitute flumes for ditches. According 
to Wimmler, sod lining often is used in frozen muck in Alaska, sometimes 
with entire success. 

Very few ditches have been built in recent years, and no modern 
costs are available. Many methods are available for such work, ranging 
from hand-shovel and pick w'ork to excavation by power shovel or 
mechanical ditchers. A common method is to plow the surface and exca- 
vate as near to grade and correct section as possible with teams and scrap- 
ers, then finish by hand. Some instances have been noted where 
hydraulic giants were used for ditch excavation. This, of course, is pos- 
sible only when water is available from a higher ditch line. Incidentally 
the hj'draulic miner uses high-pressure water for excavating wherever 
practicable. 

The alinement of ditches should be such that excavation to grade 
will provide just enough bank material to form a channel of the desired 
size. Wherever the water level is to be above the original ground surface 
it is w^ell to plow the surface before excavation starts to form an impervi- 
ous joint between the bank and ground. If the material is not such as 
to form tight banks it may be advisable to excavate the entire water 
section below the original surface. The grade must be maintained 
exactly and the desired section adhered to as closely as possible, as all 
irregularities have a retarding effect on the flow. Curves should be made 
smooth and regular for the same reason. 

If there is danger of water from floods or other sources filling the 
ditch beyond capacity, spillways must be provided at intervals to prevent 
breaks in the line which would stop operation and be costly to repair. 

2 Peele, Robert, Mining engineers' handbook, 2d ed., p. 2147, John Wiley & Sons, 



98 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. V.]') 

Measuring Weirs. The simplest method of accurately measuring a 
flow of water in a stream or ditch is by means of a weir. Numerous types 
of weirs are used, and there are many formulas for calculating the flow 
over weirs. 

The width of the weir notch should be at least six times the depth of 
the water flowing over the crest. The bottom of the notch should be level 
and the sides vertical. The weir notch is beveled on the downstream side 
.so as to leave a .sharp edge on the upstream side. The weir should be 
installed so that the water in the ])ond above is comparatively .still. It 
must also be high enough so that there is free access of air to the under- 
side of the ovei-flow slieet of water. A stake is driven in the pond 5 or 6 
feet above the weir with the top of the stake level with the notch of the 
weir. The depth of flow over the weir is measured with a rule or square 
placed on top of the stake. The Francis formula is commonly used for 

calculating the flow. 

Q - 3.33 ud 3/2, 

where 

Q — quantity of water in cubic feet per second, 

w = width of notch in weir, 

d — depth of water going over weir. 

Flumes 

As already stated, most hydraulic-mine ditch lines contain some 
flume sections. Flumes may be necessarj^ where the line passes around 
cliffs or over ravines or desirable over porous or shattered ground where 
a ditch would lose mucli water or tend to cause slides. On steep hill- 
sides or where ditching would require much costly rock excavation a 
flume may prove economical ; finally, the cost of the line may be lessened 
and considerable saving made in the total fall by building a flume or 
trestles across valleys instead of ditching the greater distance around 
the head. 

The same conditions should be considered in designing a flume as 
in designing a ditch, and the Kutter formula applies equally to both. 
The formula is used most conveniently in the form of tables or charts. 

The low friction coefficient of board flumes may be used to advantage 
either by building a flume of smaller section or by decreasing the grade 
below that of the ditch line. If the latter is done a saving in head may 
be made at the mine. Usually, however, smaller sections and higher 
velocities are used than for the ditch line. The width of the flume should 
be twice the water depth and a freeboard of 1 to 2 feet allowed. Accord- 
ing to Egleston^ the usual water velocity is 3 to 6 miles per hour (4 to 9 
feet per second) . The same author gives the range in grade of 28 promi- 
nent California flumes as 9 to'l8§ feet per mile. The extreme range of 
86 well-known flumes in the Western States was 5 to 53 feet per mile, the 
usual range 10 to 18. and the average slightly under 14. Bowie* states 
that grades of 25 to 35 feet per mile are used where practicable. Such 
steep grades would permit the use of a relatively small flume section, 
but the authors believe that usually they would involve inconveniently 
high velocities; moreover, a longer flume would be required to give the 
same head. 



• Egleston, Thomas, The metaUurgy of silver, gold, and mercury In the United 
States, p. 152, John Wiley & Sons, 1890. 

« Bowie, A. J.. A practical treatise on hydraulic mining In California, p. 143, 
D. Van Nostrand Company, New York, 1889. 



Sec. I] HYDRAULIC MINING 99 

The construction of wooden flumes has changed little since the early- 
days of placer mining in California. The flume was built in 12- or 16- 
foot sections of 1^- to 2-inch lumber, 12 to 24 inches wide. The longi- 
tudinal joints were made tiglit by nailing over each a batten ^ inch thick 
and 3 or 4 inches wide. A flume 34 by 24 inches built about 1930 for 
water power carries about 600 miner's inches on the flat grade of one- 
fifth foot per 1,000 feet and would serve excellently for a small hydraulic 
water-supply line. It differs in construction from the other type chiefly 
in having splines between all the boards of the boxes and lacking framing 
in the sills and caps. It was built over 6,800 feet of rugged country at 
a total cost of $2.50 per foot. 

AVhere the flume is on grade the box units should be set on stringers 
laid on a carefully cleared and graded surface or on a bench cut in the 
hillside. Trees or branches that might fall and wreck the flume should 
be removed. In cold climates the flume may be covered and heaped with 
earth to prevent freezing. AVhere the flume is on trestles a walk must 
be provided ; usually a line of plank is nailed over the caps or on alternate 
sills extended a couple of feet to one side of the box. The grade must be 
uniform, and at curves the outer edge of the flume should be raised suffi- 
ciently for the smoothest possible flow of water, the elevation being deter- 
mined by trial. Three-foot iron placer pipe cut in two lengthwise has 
been used successfully for flumes at placer mines in British Columbia. 

Diversion Dams and Reservoirs 

Diversion dams for hydraulic ditch lines usually are of earth-filled 
timber cribs or rock-filled cribs faced with boards. Small streams often 
are dammed by throwing logs across and facing the upstream side with 
boards. Diversion dams usually are only a few feet high but should be 
built where possible on solid rock or hardpan, sufficiently wide to be 
stable and provided with suitable spillways to prevent erosion and scour- 
ing out of the foundation. 

At mines where the water supply is insufficient for 24-hour operation 
or where the stream flow is less than is needed to operate at the desired 
capacity for one shift, reservoirs often are used." If it is impracticable 
to have the resevoir in the stream itself above the diversion dam, it is 
usually located at the lower end of the ditch, just above the intake to the 
pipe lines. Keservoirs may be built by damming a canyon, by excavating 
a basin on level ground, or merely by enlarging a section of the lower end 
of the ditch. As a reservoir break might be disastrous to a mine lying 
directly below it, the work should be done carefully, all leakage checked, 
suitable gates and spillways provided, and regular inspection maintained. 

As both diversion dams and reservoirs tend to act as settling basins 
it may be convenient to provide gates close to the bottom through which 
sediment may be flushed as often as necessary. 

Mining Equipment 

The chief items of equipment used in most hydraulic mines are pipe 
lines to carry the water under pressure to the places where it is used ; 
giants.or monitors for cutting, washing, and driving the gravel ; derricks, 
winches, or other machinery for handling boulders ; and sluice boxes for 
saving the gold and disposing of the tailings. Picks, shovels, and forks 
are the common hand tools used at placer mines. Power drills run by 
compressed air or steam may be used if the gravel contains an excessive 



100 



PLArKR MININO FOR GOLD IN CALIFORNIA 



[Bull. 135 




riu. .i:i. Pipe installation, ^2- aii'i 54-incli. Photo hy l,ih, c, .s/, of Suttnaou 
Miniiiff Cotporutioii : rei)rintC(l Jrvin CuUjornia Journal of Mines and Geoluffy, 
January I'Jil, p. 56. 



quantity of large boulders. However, hand drills are used at most mines 
to drill boulders and sometimes to drill cemented gravel or hard-clay 
strata. Churn drills are employed occasionally for drilling cemented 
gravel ahead of hydraulicking. 

Pipe Lines 

Pipe. As described pi-eviously, ditch lines are used to bring the 
necessary water to a convenient point above the mine. From that point 
a pii)e line is laid down the hillside to the pit. Occasionally, wiiere the 
grade of a creek is steep, the water will be diverted from the stream 
directly into a pipe line. Although wooden stave pipe is u.sed at a few 
projierties, steel pipe is preferred at nearly all hydraulic mines. 

Pipe may be made from steel sheets in the mine shops or bought from 
l)il)c manufacturers. I'nless a large quantity of pipe is to be used or 
transi>ortation is difficult, it usually is more economical to buy the pipe 
already made jjp. Various types of steel pipe are used, but light-weight 
riveted pipe with slip or .stove-pipe joints generally is preferred in the 
Western States as it is cheaper, lighter, and more easily transported and 
installed than other steel pipe. 

Sj)iral i-iveted ])ipe will stand greater pressures and harder usage 
than the straight riveted pipe, but it is more expensive. Moreover, 
flange joints, which are an added expen.se, generally are used with the 
spiral pipe. Ordinary riveted pipe of 10 to 16 United States standard 
gage material 7 to 46 inches in diameter was being used in western mines 
in lU.Ti; the diameters used most were 3G, 32, 24, 22, 18, 15, 11, and 
9 inches. Large pipes are easily damaged if made of material thinner 
than 14 gage. Usually two or more diameters and gages of pipe are used 



Sec. I] 



HYDRAULIC MINING 



101 



Table J/. Maximum quanlity of slip-joint water pipe that can he loaded on flat car 
8 feet 6 inches wide by .'/O feet long, using side stakes 10 feet high 



Diameter, inches 


Maximum number 


Sections 


Feet 


4 


1,152 

760 

544 

420 

310 

264 

220 

180 

144 

128 

112 

98 

84 

60 

60 

40 

40 

40 

30 

30 

30 

30 

30 

10 


22 320 


5 


14 725 


6 


10 540 


7 


8 137 50 


8 


6,006.25 


9. 


5,115 


10 . 


4,262.50 


11 


3,487.50 


12 --- -- 


2,790 


13 - 


2,480 


14 


2,170 


15 ..- 


1,898.75 


16- . . 


1,627.50 


18- 


1.162.50 


20 


1,162.50 


22 


775 


24 


775 


26 


775 


28 


581.25 


30 


581.25 


32 


581 25 


34 


581.25 


36 - 


581.25 


48 


193.75 









in the same line, mainly as a matter of convenience since this permits 
nesting in transit. A saving may be made in ocean freight and occa- 
sionally in truck hauls by nesting the pipe. 

Slip-joint pipe is made in standard lengths of 19 feet 7^ inches each. 
The sections may be made longer or .shorter, however, as required bj"- 
transportation purposes, provided they are in multiples of 4 feet. The 
extra pipe required for a slip joint is about 3 inches per section. The 
standard length of sections of spiral riveted pipe is 20 feet. Placer pipe 
usually is coated inside and out with an asphalt paint. 

A pipe of smaller diameter will withstand a greater pressure than a 
larger pipe of the same wall thickness; therefore, it is common practice 
to use smaller diameters as the pressure increases. Reducing the diam- 
eter increases the friction in the pipe, and a balance must be struck 
between loss of effective head in the pipe line and first cost of the line. 
Branch lines usuall}' have a smaller diameter than the main supply lines. 

The minimum carload weight is 20,000 and the maximum 80.000 
pounds in California. Carload shipments take fifth class rate. Less 
than carload shipments of pipe up to 12 inches in diameter take third 
class and over this diameter one and one-half times the first-class rate. 

As used pipe is available in nearly all placer districts, very little new 
pipe is purchased except for installations of some magnitude. There are 
no established prices for used pipe. 



102 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

The Y's and T's needed for branch lines usually are purchased from 
the pipe manufacturers. A header box may be used when more than two 
branches are taken out at one place. 

Joints and Valrcs. In makinpr the pipe with slip joints the diameter 
of one end is slipfhtly contracted. This joint in straight pijie lines will 
withstand most pressures encountered at placer mines. Slip joints, how- 
ever, become battered from frequent layinj,', and other types are desirable 
wliere the pipe is moved often. 

Flanged or bolted joints are used in some pits for siphons and in very 
high -pressure lines. The Taylor flanged joint is of forged steel and is 
welded to the pipe ; the price includes bolts and gaskets. The 8-inch size 
is good for a working pressure of 200 pounds; 8- to r2-inch size, 125 
pounds ; 12- to 20-inch size. 110 pounds ; and above 20-inch size. 75 pounds. 
The American flange also is complete and attached to the pipe. Most 
sizes are good for a working pressure of 300 potnids per square inch. 

Sometimes a lead joint is used ; this consists of a sleeve three-fourths 
of an inch larger than the pipe, placed around the two ends to be con- 
nected. The space between the ring and pipe is filled with molten lead. 

Riveted elbows furnished by the pipe manufacturers generally are 
used for making turns in pipe lines. Taper joints are used where reduc- 
tions are made in lines. Sudden reductions in size are to be avoided 
because of the loss of head and strain on the line. 

Standard valves are used for diverting water or closing off flow in 
pipe lines. Valves should be closed slowly and with great care in high- 
pressure lines; the pressure exerted by the sudden stoppage of flow in 
the water column may burst the pipe. 

Air vents are needed at all crests in hydraulic pipes to prevent a 
vacuum being formed and subsequent crushing of the pipe. Venting 
also is necessary to prevent air pockets in the line. The device consists 
of a leather-faced flap on a hinge bolted on the inside of the pipe. A bail 
attached to the flap goes through an oblong hole 1^ by 3 inches in size, 
cut in the pipe. As the water fills the pipe the flaj) fits tightly against 
the inside ; as the water falls the flap drops, making a vent. 

Pressure Boxes. To give the water entering a pipe line an initial 
velocity pres.sure boxes or penstocks are used. A head of 4 to fi feet 
u.sually is provided. A length of large-diameter pipe may be used at 
the top of the line instead of a penstock. A screen usually is placed at 
the head of the line to keep out trash. In some installations settling 
boxes are provided where solid matter may settle out before the water 
goes into the pipe, as such material may cause rapid wear of the nozzles 
of the giants. 

Laying Pipe Lines. Pipe lines are laid by begiiniing at the bottom 
and working upward. Sharp curves are avoided wherever possible, and 
where used the pipe must be anchored securely to prevent the thrust of 
the water pressure from pulling the joints apart. Curves in a vertical 
plane are especially undesirable as they may cause air pockets in the 
pipe. The pipe .should be filled gradually for the same reason. In 
crossing small ravines a trestle should be built first and the pipe laid on 
plank for the complete distance. 

In laying new pipe with slip joints the outside pipe is started over 
the end of the other, then heated with a blow torch, which expands the 



Sec. I] HYDRAULIC MINING 103 

outer pipe and melts tlie tar previously placed on the end of the lower 
pipe. As the heating is completed the upper pipe is driven home by 
hammoriufr on a block of wood placed at the upper end. The tar makes 
a water-tif^ht connection. Where the pipe has been battered from previ- 
ous handling?. burla]> or sackinj^ may be wrapped around the joint before 
drivinjj. If leaks develoji they may be stopped by drivinj; in wooden 
plugs; .sometimes an outside band is recpiired. 

In placing pipes with flanged joints they arc laid end to end and the 
bolts put through and tightened up. TheHanges usually are attached 
to the pipe at tlie factory. This prevents nesting of the pipe in shipping 
but permits a better joint to be made. 

When pressures are very high or when the pipe has vertical or lateral 
curves, lugs should be riveted on the ends of the pipe with slip joints and 
the two pipes wired together after the connection is made to prevent the 
joint pulling out. Similar lugs can be used for anchoring the line to 
stumps or posts. 

In straight pipe lines expansion joints .should be placed at intervals 
of ]()() to 2,000 feet, depending upon the conditions to be met. Where 
pipe lines have lateral curves expansion joints are not needed, as the 
expansion or contraction of the pipe is taken up in the curved sections. 
A long, empty pipe line may contract several feet between a warm day 
and a cold night, and unless provision is made for this contraction the 
pipe will pull apart. AVhen the i^ipes are kept full of water this con- 
traction does not occur. Pipe lijies are buried in .some locations but 
seldom at western placer mines. 

The cost of laying pipe lines depends upon the size of the pipe and 
the topography and cover of the country. Ten men working 90 days laid 
5,000 feet of 36- to 16-inch pipe at the Browning mine, Leland, Oregon, 
in open country in the spring of 1932. 

Flow of Water Through Pipci. The quantity of water that will flow 
through a pipe line at a placer mine depends mainly upon the diameter 
of the pipe, the effective hydraulic head, and the size of the nozzle used 
on the giant at the end of the pipe. Generally the nozzle u.sed is of such 
a size that the pipe will carry the available water. As the water supply 
is reduced smaller nozzles are used on the giants. 

The effective head on a pipe is the static head minus the loss of head 
caused by friction. The loss of head depends upon (1) the velocity of 
the water, (2) the roughness of the interior of the pipe, (3) the diameter 
of the pipe, and (4) the length. The pressure available and the amount 
of flow at the end of a long pipe depends mainly upon the last three items. 
The pressure of the water in the pipe has no effect, by itself, on the loss of 
head. Formulas have been derived for calculating the loss of head in 
Avhich coefficients of roughness are used. These coefificients have been 
derived by experiment for different types of pipes; specifically, however, 
consideration must be given to the service conditions oicountered. No 
standard of roughness exists, and the degree of roughness of the interior 
of a pipe does not remain constant. Usually a pipe is chosen about 20 
percent larger than would be indicated if there was no loss due to friction. 
Flow through an unobstructed pipe line of uniform diameter can be 
calculated from a number of formulas. The Kutter modification of the 



104 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 





Fio. 30. Small giant In operation. Extra water (by-water) for sluicing In back- 
ground. Photo by C. V. Averill. 



Sec. I I llYDRArMC MININO 105 

Cliezy formula appears to be preferre<l by bydraiilic eii<>ineers. Tbe 
Cliezy formula may be stated as: 

Tlie Kutter moditicatiou of tlu' Cbe/y formida is: 

1.S11 0.0()2S1 

+ — ?; — + -H<'« 



V = \/h'8 



where 

T — nu'iiii vclcicity of flow, feet per scfoiul ; 

C = "cootticient of rotanljition," so-Ciillrrl ; 

If = moan hydraulic radius of the pijic, that is, } the diameter in feet ; 

,V = hydraulic ^'i ado or slope, in foot i)or foot of lon};th of a pipe of uniform size ; 

n = "co(>tticiont of ronjrlmoss," so-callod. 

The value of n for riveted lap-joint pipe up to and including | inch 
thick can be taken as 0.015. 

Giants 

A priant or monitor is a device -with a nozzle for directiuf^ and con- 
trolling; a stream of water under a hydraulic head. The fjiant can swing 
horizontally through a full circle and from 11° below to 55° above the 
horizontal. A box of stones is used to counterbalance the weight of the 
spout. A giant generally is set up in a pit by being bolted to a log or to 
timbers securely anchored in bedrock. Nozzles of different diameters 
can be used up to the diameter of the outlet of the giant to make allow- 
ance for variation in the quantity of water used. The giant and nozzle 
are constructed so that a rotary motion of the jet is prevented, and the 
water is discharged in a solid column. Giants are made for a wide range 
of service in 10 sizes, numbered to 9, inclusive. 

With heads of 100 feet or more deflectors are used for pointing the 
larger giants. A common type of deflector consists of a short section of 
pipe that projects over the nozzle. It turns on a gimbal joint and is 
controlled by a lever. As the deflector is turned against the jet the force 
of the stream turns the giant in the opposite direction. 

Table 5 shows the sizes, weights, and prices of giants and deflectors 
made by one manufacturer. ■' Other companies make similar equipment 
at competitive prices. 

Discharge Through Nozzles. Table 6 gives the discharge through 
different sizes of nozzles under heads from 100 to 400 feet. In this table 
40 miner's inches is considered as 1 cubic foot per second. The theoret- 
ical floAv of water through nozzles exceeds the figures in table 6 by about 
10 percent; allowances have been made for friction losses. The flow 
through nozzles not shown in the table or for different heads can be cal- 
culated from the equation : 

where ^•'^^^'-'^ ^^ 

Q = cubic feet per second, 
A = area of nozzle (square feet), 
/, = effective head at nozzle (feet), 

(' =^ coefficient of discharge rauRing from 0.8 to 0.94 (usually taken as 0.9, which 
makes allowance for friction). 

To convert cubic feet to gallons multiply by 7.48. 



6 Joshua Hendy Iron Works, San Francisco, California. 



106 



PLAPKR MINING FOR fJOLD IN CALIFORNIA 



[Bull. l:J5 



Tnhic .7. Si;ri>, utifihln. and jirirrx of ilouhjc- jointed, linUlirnring giants 
and deflector a 









Giants 






Deflectors 






w 

i 1 






55 

II 


List 


price* 


1 


X 


Siie t»o. 


3 

1 

1 


5"? 
1 ^ 







5 
7 
9 
11 
11 
13 
15 
15 
18 
18 


3 
4 
5 
6 
7 
8 
9 
10 
10 
11 


350 

390 

520 

890 

1.075 

1.475 

1.850 

2.100 

2.300 

2.450 


105 
120 
150 
210 
225 
335 
520 
520 
600 
690 






(') 
30 
40 
45 
55 
70 
75 
80 
80 
90 




1 


$180 
225 
320 
365 
485 
620 
725 
850 
925 


$165 
210 
295 
330 
460 
580 
685 
805 
865 


$29.00 


2 


32 00 


3 


37.00 


4 


40.00 


6 


56.00 


6 


62.00 


7 


67.00 


8 


67.00 


9 


71.00 







» Subject to discount because of fluctuations in prices of iron and steel. 
» None required. 

Elevators 
Ruble Elevators 

The Ruble elevator is named for the Ruble mine in Josephine 
County, Ore. It consists essentially of an inclined grizzly on a pitch of 
about 17", up which the gravel is driven by the stream from a giant. The 
oversize goes over the grizzly to a ruck pile, and the undersize runs down 
a chute under the grizzly and thence into sluice boxes, u.sualiy set at right 
angles to the elevator. The spacing between bars of elevators in use in 
1932 ranged from ^ to 2h inches. A 10- or 12-foot apron is used in front 
of the grizzly. The gravel generally is swept to the foot of the elevator 
by one giant and through the Ruble by another. The gravel must be 
washed thoroughly before it is elevated, and the stream of the elevator 
giant must be used with caution; otherwise, considerable gold may be 
driven over the top. 

Under favorable conditions one giant can handle as much material 
through the Ruble as another can cut and sweep to it. Under other con- 
ditions less than half of the material can be put through the Ruble that 
one giant working steadily can get to it. 

Hydraulic Elevators 

Hydi-aulic elevators are used to rai.se ^fvavel. .sand, and water out of 
placer |)its into sluice boxes. An elevator consists of a pipe with a con- 
stricted port or throat and a jet which provides a high-velocity ascending 
column of water. The relative diameter of pi])e. throat, and'jet must be 
proportioned according to the conditions under which the elevator is 
used. The elevator may also be used as a water lifter. 



Sec. I] 



HYDRAULIC MINING 



107 



Tabic 6 


Flow of %oa 


ter through giants * 










j 2. 


Effective head, feet 




100 


200 


300 


400 


Giant no. 


a. 




4 

H 

a. 


5-1 


4 

Is" 

2 "^ 


If 


.1 


2 

?' 





2 
3 
3 
4 
3 
4 
4 
6 
5 
6 
6 
7 
6 
7 
7 
8 
9 
10 


0.6 
.8 
1.6 
3.0 
3 3 

5 6 
3.7 
6.0 

6 3 
13.3 


22 
33 
63 
120 
133 
227 
148 
240 
253 
53=i 


0.8 

1.2 

2.2 

4.3 

4.7 

8.3 

5.0 

8.6 

8.9 

19.2 

13.9 

19.3 

19.6 

26.7 

20.0 

26.9 

27.2 

35.3 

45.0 

55 3 


31 

47 

89 

173 

187 

333 

200 

343 

357 

770 

560 

770 

780 

1,070 

800 

1,080 

1,090 

1,410 

1,800 

2 210 























2.7 
5.3 
5.7 
10.3 
6.5 
10.6 
10 9 
23.7 
16.7 
23.8 
24.1 
33.2 
24.5 
33.3 
33.8 
43.7 
55 3 
68.2 


109 

213 

227 

410 

245 

423 

437 

950 

670 

950 

960 

1,330 

980 

1,330 

1,350 

1,750 

2,210 

2,730 


3.1 
6.4 
6 6 
11.9 
7.1 
12.2 
12.6 
27.5 
19.7 
27.7 
27.9 
37.7 
28.3 
38.0 
38.3 
48.7 
63.7 
78.7 


125 


J 


257 


2 


267 


2 


477 


3 


283 


3 


488 


4 


504 


4 


1.100 


5 


9 8 30n 


790 


5 . 


13 5 
13.8 
18.7 
14.2 
19 
19.2 
15.2 
32.0 
39 3 


540 

550 

750 

570 

760 

770 

1,010 

1,280 

1,570 


1,110 
1,120 
1,510 


6.. . 


6 


7 


1,130 


7 


1,520 


8 


1,530 


8 


1,950 


9 


2,550 


9 


3,140 















1 Adapted from table in catalogr of Joshua Hendy Iron Works, San Francisco, 
California. 



The height to which gravel can be lifted is one-tenth to one-fourth 
of the effective head of the pressure water at the nozzle of the elevator. 
Usually the lift will be about one-fifth the head. 

The volume of gravel that can be handled by an elevator depends 
primarily upon the head and volume of pressure water available and to 
a lesser extent upon the quantity of other water that has to be raised by 
the elevator. The solids in the water usually are 1.7 to 2.5 percent. 

Where little drainage water has to be handled and other conditions 
are favorable the proportion of the water delivered to the elevator and 
the giant, respectively, should be about equal, provided the pressure is 
the same in both. U.sually, however, about twice as much water or a cor- 
respondingly higher head is required for the elevator. The discharge of 
the elevator should be high enough to provide dumping ground, other- 
wise a giant may be needed to stack the tailings. Where plenty of water 
is available a compound or step-lift elevator may be installed in which 
one-third of the pressure water is used in the first lift and two-thirds in 
the second, with a correspondingly larger area of upraise pipe. Thus, 
the height of the lift may be nearly doubled. Double lifts sometimes are 
used ; that is, the discharge of one elevator goes to the intake of another. 



108 



PLACER MINING FOR GOLD IN CALIFORNIA 



[Bull. 135 



End section is buitt as separate 
" " " for moving 




Sluice boxes take Solid steel lined floor 
out from here to here; grizzly above 




Pl-AN 



Grizzly of Y* 6' 

edge, capped witti steel 

straps, spaced " 



Ftoor steel-lined 



TRANSVERSE SECTION LONGITUDINAL SECTION 

36. Ruble elevator used at Redding Creek mine, Douglas City, California. 




The elevator discharges upon a cover plate to take the wear in the 
head of a sluice. Boxes may or may not be used in the pit. The size of 
the gravel handled is limited by the size of the throat of the elevator. 
Grizzlies generally are used at the intake. Coarse material reduces the 
capacity of the elevator; sometimes a Ruble elevator is used in the pit, 
and only the under-size is sent to the hydraulic elevator. 

In clayey ground a hydraulic elevator tends to break up the clay as 
it goes through the elevator, tluis permitting a higher extraction of the 
gold. 

Gravel pumps have been used successfully in alluvial tin mines and 
in at least one placer mine in British Columbia." As far as known, they 
have not been used successfully in placer mining in the Western States. 

Hydraulic Mining Practices 

Conditions varied widely at the hydraulic mines operated in the 
Western States in 1932. The practices at these mines illustrate the dif- 
ferent pha.ses of hydraulic mining and are discussed in this paper. In 
earlier days, however, when the large hydraulic mines of the West were 
being worked, more elaborate equipment and larger installations were 
used than at present. Higher banks were worked, and very large daily 
yardages were washed, with correspondingly lower costs. 

w. . 'Operations of B Boe on Cedar Creek, Quesnel District: Ann. Report of the 
Minister of Mines of British Columbia. 1932, p. AH2. 



Sec. I] HYDRAULIC MINING 109 

Gravels 

The {Travels being worked at liydraulic placer mines in the summer of 
1982 ranged in average depth from 5 to 100 feet ; at Relief Hill, where an 
old mine was being reopened, the depth was 200 feet. The condition of 
the gravel ranged from soft, easily washed material to gravels that had to 
be loosened by blasting. The percentage of boulders over 1 foot in diam- 
eter ranged from less than 1 to 20. TTsually, 5 to 15 percent of all mate- 
rial handled consisted of boulders. Boulders up to 20 inches in diameter 
were put through the sluices. Clay constituted zero to 15 percent of the 
total material. At. one mine, the Elephant, 2| feet of gravel was over- 
lain with 40 feet of volcanic ash. 

Bedrock at nearly all mines was soft, and the top could be piped off 
in cleaning up. The slope of the bedrock ranged from ^^ inch to 2 inches 
per foot. 

Water Supply 

Very few hydraulic mines can operate tlie entire year. Advantage 
generally is taken of higli-water periods for working the mine. In Cali- 
fornia the season may begin in November or December, when the winter 
rains commence, and continue into the dry season of June or July. At 
most California mines the winter temperature is not low enough to inter- 
fere seriously with placer operations. Elsewhere in the West, however, 
hydraulic placer mining must cease with the advent of cold weather in 
October, November, or December. At such places, work can not begin 
until spring when the snow melts and the ground thaws. In many local- 
ities placer mining can be carried on only while the snow is melting on 
the mountains above during the spring months. The length of the 1932 
season at the mines visited by the authors ranged from 25 to 225 days. 
The precipitation during the winter of 1931-32 was normal or above nor- 
mal in nearly all districts; immediately preceding years, however, were 
dry, and the number of days operated at the majority of places was much 
less than in 1932. In exceedingly dry years some mines do not have 
enough w^ater to operate at all. 

Reservoirs are used at most mines. As the flush supply gives out 
the water may be stored and used periodically for mining. Usually 
cutting operations cease when water is not available for piping at least 
1^ or 2 hours per day. The dwindling supply then will be used for 
cleaning bedrock and cleaning up the boxes. 

Water rights in most of the older placer districts have been adjudi- 
cated. The rights of some old placer companies are still intact, and the 
water can be used without hindrance for operating these mines. How- 
ever, other water rights in streams have been obtained by power or 
irrigation companies, and water for placer mining must be acquired from 
those controlling the rights. In some instances, however, water can be 
appropriated for placer mining. 

As stated before, water under a relatively low pressure may be used 
for undercutting a bank to assist ground sluicing. Generally, however, 
a head of at least 40 feet must be available for hydraulicking sand and 
loam and the easiest cutting gravel. An 80- or 90-foot head usually is 
required to cut average gravel banks. When the gravel is tight or con- 
tains boulders a head of at least 125 feet should be available for hydrau- 
licking. For very tight or cemented gravel, heads over 200 feet should 
be available. Higher heads give greater cutting and driving power to 
the giants and thus increase production. High pressures are necessary 



no 



PLACKR MINING FOR GOLD IN CALIFORNIA 



Bull. 135 




°: 

S3 

<U 05 



SQ 



Se.- 



nYOKArijic MiMxr, 



111 



Manganese-steel hood- 



^/sy//s///:-^^ 




Fio. 38. Hydraulic elevator. 



112 PLAfFR MINING FOR GOLD IX CALIFORNIA | Rllll. 1 ;{r» 

for hi^rli hanks, as the piants must be set far enougli away tliat caving 
pravel will not injure the workmen when the banks are undercut. The 
extreme ran<re of the heads on the jjiants at tlie mines was 40 to 450 feet. 
The usual ranjie was 100 to 800 feet. 

In at least 7") percent of the 40 or more operating hydraulic mines 
visited in lIKi'i water was conveyed in ditches dug by the early miners. 
Often, okl pipe lines or salvaged pipe were utilized. Some of the present 
lines are built of pipe first installed 50 years ago. "Water was pumped at 
four mines. Pumpinj; water for hydraulicking, however, lias not been 
generally successful. 

The pipe ranged in size from one line with an intake diameter of 46 
iiu'hes, wliich was reduced by stages to 24 inches in diameter at the pit, 
to lines of lO-inch pipe. 

Reservoirs where used ranged in size from 0.01 to 15 acre-feet. 

Didif of Wafer. The duty of a miiuM-'s inch of water in hydraulick- 
ing is defined as the number of cubic yards of gravel which it can break 
down and send through the sluice in 24 hours. The factors atfecting this 
duty are so varied that it can be compared directly at few mines. An 
average duty of a miner's inch can not be calculated for the same rea.son. 
The duty of water appears to be highest in large-scale operations. Tight 
or cemented gravel is difficult to break down; a high bank takes less 
pressure water per cubic yard than a low one; a flat bedrock requires 
an excessive quantity of water for sweeping; angular rock and gravel 
with flat or large boulders requires more water to move it than does small- 
size, rounded material ; clay-bound gravels require excessive washing to 
free the gold; high water pressure is more effective than a low one for 
cutting or sweeping; and the grade and size of sluices govern the daily 
yardage that can be washed through them. The calculated duty of water 
at the mines operating in 10;{2 ranged from 0.4 to 4.3 cubic yards per 
miner's inch. In these calculations by-wash water is included. 

Conditions at the mines range from the most difficult to at least 
average. Wimnder" reports a duty of as higli as 10 cubic yards per 
miner's inch at some Alaskan placer mines; the usual range, however, 
was about 0.5 to 1.7 cubic yards per miner's inch per 24 hours. 
Piping 

After a mine is opened up the gravel bank is undercut by the giant, 
which allows the overlying material to cave into the pit. The fall breaks 
the gravel to some extent ; it is further reduced by being played upon 
by the stream from a giant or by by-wash water. As the gravel is being 
disinte-rrated it is swej)t by the giant toward the sluice box. Where the 
gravel is clay-bound or contains lumps or streaks of clay it may be washed 
back and forth acro.ss the pit bottom one or more times until free from 
tl»e clay. 

A smaller-diameter nozzle generally is used for cutting than for 
sweeping. As an example, a quantity of gravel may be brought down 
wijh a giant witli a 4J-inch nozzle. Then the water will be shut off and 
a 5-inch nozzle put on the giant for driving the gravel to the sluice, or a 
separate giant witli a 5-inch nozzle can be used. Usually two or more 
giants are set up in a pit even when only enough water is available to 
run one at a time. One large giant will do more work than two small 
ones using the same quantity of water. The giants are placed at the 

'^'.TlfL^'"' ^''o»'"ian L., Placer-minitiB methods and costs in Alaska: U. S. Bur. 
Mines Bull. 259, p. 139, 1927. 



Sec. I] HYDRAULIC MINING 113 

most strategic points both to cut the bank and wash the gravel to the 
sluice box. Where two giants are used at a time one may be used for 
cutting and the other for sweeping. The cutting giant is set on an angle 
to the face. At the old La Grange mine the streams from two 9-inch noz- 
zles were used together for both cutting and sweeping. Giants may be 
set up at the lower end of the sluice to stack the coarse material in the 
tailings where the grade is not sufficient for it to be disposed of naturally. 

Sometimes a pit is laid out so that all of the gravel washed in one 
season is swept to the head of the sluice. After the clean-up the boxes 
are extended through the washed-out pit and set up for the next year's 
work. At other places the boxes are extended upward as room is made. 

When a pit is started a cut is taken across the channel, after which 
a diagonal or square face is advanced upstream. In wide channels or 
bars two or more parallel cuts may be taken. One pit may be worked 
while boulders are handled or bedrock is cleaned in the other. At the 
Ruby Creek mine at Atlin, British Columbia, the channel was 250 feet 
wide; two 125-foot cuts were made and worked alternately.^ Wing 
dams of timber, logs, or boulders generally are built to guide the water 
and gravel into the head of the sluice. 

Occasionally the form of the deposit and the contour of the bedrock 
are such that the gravel is washed over the side of the boxes rather than 
into the end. Then the sluiceway is sunk into bedrock. 

At some mines overburden containing little or no gold may be mined 
separately. This system has an advantage when dump room at the end 
of the main sluice is limited, as the higher material may be disposed of 
elsewhere. At one mine, the Salmon River, the light top material was 
stripped after the water supply was too low for working the heavier 
gravels but was still sufficient to supply one giant. The usual practice, 
however, is to mine the full thickness of gravel at one time. The admix- 
ture of the top soil and light gravel with the heavier material from near 
bedrock may permit moving a larger proportion of boulders to the sluice 
than otherwise. 

The number of giants used at one time in the mines operating in 
1932 ranged from 1 to 4. The size of the giants ranged from nos. 1 to 6 
and the diameter of the nozzles from l^ to 7 inches. A larger nozzle is 
used for sweeping than for cutting in about half of the mines and the 
same size in the other half. In one mine, the North Fork placer, water 
used for sweeping came from a separate source under a lower head ; a 
smaller nozzle was used than for cutting where the pressure was higher. 
The nozzles used in the elevators ranged from 3^ to 4 inches. The dis- 
tances that the material was elevated were 25, 44, 54, 17, 30, 9, and 19^ 
feet. The distances the coarse material was elevated by Ruble elevators 
were 14, 25, and 11 feet. 

Handling Boulders 

Where the size and grade of sluices permit, all boulders that can be 
moved by the giant are run through the boxes. As stated before, the 
upper limit in size at present mines ranged from 4 to 20 inches in 
diameter. At some of the early-day large producers boulders weighing 
3 or 4 tons were successfully put through the sluices.^ 

» Lee, C. F., and Daultin, T. M., The .solution of some hydraulic mining problems 
on Ruby Creek, British Columbia : Am. Inst. Min. Met. Eng. Trans., vol. 55, p. 90, 1917. 

eMacDonald, D. F., The Weaverville-Trinity Center gold gravels, Trinity County, 
Calif. : U. S. Geol. Survey Bull. 430, pp. 48-58, 1910. 
8 



114 



I'LACr.R MININC I\)K (;OI,n IN CALIFORNFA 



ir.iill. i:}.") 




Kic:. V.K IfamlliiiK lioiild.rs witli iliTiick. I'liol,, bi/ C. V. AvrrWl. 



Ill <ri-<)iiii(l sliiiciii'-- any Ixiuldo- that can Ix' washed into tlie sluice by 
the water usually <;<h's throu-ih without trouble. In hydrauliekiiifz', \\u\\- 
ever, boulders too larjie to run tlii-ouj:li the sluice may be swejit into it 
with a larti:e j?iaut usiu-r a bi^ih head of water. IJouldei's too lar<i:e to be 
moved by the j,naut or to run tln-ou«ih the sluice are handled in various 
ways, dependiu«2: luaiidy upon the nundier and size of the boulders 
encountered and the nuijrnitude of the operations. 

In small-scale operations boulders may be rolled by hand to one side 
or onto cleaned-U]) bedrock, or (lra;i<ied away by teams. Occasionally, 
a boidder t(jo larjre to handle may be left standing- on the floor of the pit 
and bedrock cleaned uj) around it. The usual custom when the proportion 
of bouhlers is small, however, is to break them up by nutans of hannners 
or by blasting; and wash the fra«iinents throu<:li the sluice. In the larger 
operations with relatively shallow j:ravel, as at the Salmon Kiver mine, 
the boulders may be pulled from the pit by wiiu-hes or moved by a 
derrick mounted on a tractor, as at the Salyer mine. At the Diamond 
City mine a drag line with an oi-angepeel biu-ket handled boulders very 
cheaply under the existing coiulitions. A relatively narrow cut was being 
run. The drag line was operated on a bench above the cut ami i)iled the 
boulders on the bench back of the drag liiu\ The most connuon nu'thod of 
handling boulders, howevei', is by means of a derrick. The boulders that 
can be rolled by hand are loadecl onto a sling or a stone boat and hoisted 
from the i)it. Large ones are hoisted by means of chains. At some mines 
few boidders that can not be nuned by the giant are encountered ; derricks 
are used at tlie liead of the sluice for i-emoving those too large to go 
through. Stumps are handled in miu-h the sanu» manner as boulders. 

Cleaning Bedrock 

BedrcK'k usually is cleaned by i)i|)ing. As much as 2 feet of bedrock 
may be cut by the giant and the nuiterial washed through the sluice. 
Occasionally a fire hose with a small nozzle may be used for the purpose. 
When the bedrock is hard and contains crevices, it must be cleaned by 



See. I] HYDRAULIC MINING 115 

hand. The crevices and soft scams are dug out by means of small, flat 
tools made for the purpose. 

Sluice- Boxes and Riffles 

Sluice-boxes were laid on bedrock at the most of the mines being 
operated in 1932. At a few, where high chauuels were being worked, 
cuts had been run to bedrock to permit an adecpuite grade for the sluices. 
In one mine, a tunnel was used. 

Individual boxes were 12 feet long at the majority of places. In a 
few districts 16-foot boxes were jireferred, and occasionally a 10- or 14- 
foot box was used. The h^igtli of the sluice at various mines ranged 
from 32 to 5,000 feet. The long sluices generally are used only wlien 
they are necessary as tailraces. The width of sluice boxes at these mines 
ranged from 12 to 60 inches. The extreme range in the grade of boxes 
was from l inch to 1| inches to the foot (1.0 to 12.5 percent) . The n.sual 
range Avas from ] to ^ inch to the foot (2.1 to 6.2 percent). 

Riffles serve a twofold purpose, they pi-otect the bottom of the sluice 
and catch the gold. Both strength and wearing qualities are required 
in large-scale liydraulic operations where boulders up to a ton in weight 
may be put through the boxes. AVooden blocks, rails, rock paving, and 
iron castings, in the order named, were used at the larger mines operated 
in 1932. When the service was not so severe, poles, angle iron, and Ilun- 
garian-type riffles were Used. The Hungarian riffles usually were made 
of wood and were protected from wear on top by strap iron. 

At all mines most of the gold was caught in the first few boxes of the 
sluice. The top boxes were cleaned up twice a season, monthly, weekly, 
or even oftener. In long sluices the lower boxes were cleaned only at the 
end of the season or when repairs were needed. At the time of the gen- 
eral cleanup worn riffles were replaced and the sluices repaired if neces- 
sary. Quicksilver was used in the sluices at the largest mines, but at 
the majority it was used only in cleaning up. 

Although the sluice is an efficient gold-saving device some gold gets 
away, especially- if the gold is very fine and the gravel carries a relatively 
large proportion of black sand. To further recover the gold, undercur- 
rents were used at 10 mines. The term "undercurrent" in placer min- 
ing is used to designate a device for catching the gold contained in the 
fine material drawn out through a grizzly in the bottom of the sluice. 
The undercurrent usually is placed near the lower end of the .sluice. At 
most mines it is not possible to draw all of the material small enough to 
go through the grizzly to the undercurrent, as not enough water would 
be left in the sluice to dispose of the coarse material. The quantity 
drawn off is controlled by the area of the grizzly and the openings between 
the bars. The grizzly bars are i, ], iJ, 5, or 1] inches apart. Undercur- 
rent boxes, or tables as they are sometimes called, are relatively wide to 
permit a shallow depth of the .sands. 

The same type of riffle generally is u.sed on undercurrents as in sluices 
where a screened product is treated. Hungarian riffles, usually similar 
to those used on dredges, Avere favored. Steel matting or wire screen 
over burlap was used at two mines ; planks with holes bored in them, 
angle iron, and stone paving were used at one mine each ; and a variety 
of riffles was used at another mine (Salyer). Quicksilver was used on 
undercurrents at nearly all of them. An important function of an 
undercurrent in placers where quicksilver is used in the main sluice is 



pi.A( i:h minin(; for r.oi.n in cai.tfornia [Bull. 135 








K^J^' 



^^^>^ 



,S- 



*«5?V„ 









^'^^js*^ 






V 3w- 



^t»-^^ 



-:'V^ 



irK^sJ^S^i?^^ 



P'iG. -JO. Sluif.' box at liyilraulio mine, /'/lo/o (j.i/ C. V. A\*riU. 




Fig. 41. P'orkiUK Ij-.ul.leis along sluice at hydraulic 
mine. Photo by courtesy of Roy McGain; reprinted from 
California Joiii-nal of Mines and Geology, October 19il, p. 5H. 



Sec. 1 1 



HYDRAULIC MINING 



117 




Fig. 42. Stacking coarse tailing with giant; .sluice i.s under grizzly. Reprinted 
from California Journal of Mines and Geology, January 19.il, p. 50. 

to catch quicksilver or balls of amalgam that may get away in the sluice. 
As much as 10 percent of the recovered gold may be saved' on the under- 
current, but in most places less than 5 percent is so obtained. At three 
mines where an estimate Avas made, 3, 5, and 8 percent, respectively, of 
the total gold recovered was saved on the undercurrent. At two places 
so little gold reached the undercurrents that they were not cleaned up 
at the end of the 1932 season. 

The sluice-box serves a double purpose in placer mining ; it collects 
the gold or other heavy minerals sought within the riffles of the sluice 
and conveys the washed material to a dumping ground. It is an efficient 
gold saver and is universally used in hydraulicking and ground-sluicing. 
The principle of the riffled sluice is used for recovering most of the gold 
on dredges and in other forms of placer mining where the gravels are 
excavated mechanically. 

Sluices are built in accordance with the service to be demanded of 
them. Riffles are of varied forms and are made of different materials. 
Although the form of riffle is chosen largely to fit particular conditions 
custom in various districts and materials at hand have a bearing upon the 
practices followed. 

The following discussion has a general application and is not con- 
fined to any region or method of mining. 

Construction of Sluice-Boxes 

Sluice-boxes are rectangular in section and are nearly always built of 
lumber ; steel or iron sluices, however, were used at a few washing plants 
operated in 1932. The construction of a wooden sluice-box depends 
somewhat upon the size and service expected of the box; a number of 
types, however, may be used satisfactorily. 

The important features in design a^-e .sturdiness and .simplicity of 
construction. Large flumes may have to with.stand severe battering and 
vibration from the passage of heavy boulders, hence they must be strongly 
constructed and well braced. In small flumes this feature is less impor- 



118 rLACKK MININc; FOK COLD I.V CAMFOKNIV [Rllll. 135 

tiiiit. I)iit the Mso of li^'litcr linnl)or iiicrcnscs tlio (liniciiltics of iiuiintoiiaiice 
and pi'cvciitidii of leaks. 

'I'lic bottom of a iiari'ow sliiico sliould he a sinjrlo ])lank if lumber of 
tlic desired width is obtainable; for widei- boxes two or more bottom 
planks must be nsed. The bottom joints may be made tijrht by the use 
of soft-pine splines, by batten strips nailed on the outside, or by caulkinj^ 
with oakum or other material, liowie'" i-econnnends half-seasoned lum- 
ber as most suitable for the construction of boxes. AVIiere local timber 
is used it is common jiractice to cufthe plaidv durinj; the dry season or 
before snow is off the jrround. It is not customary to use surfaced lum- 
ber for boxes, althou<rh a smooth bottom facilitates the clean-up. The 
lumber slunild be cleai- and of uniform si/e. 

For any but small, tempoi-ary installations the sides of shiice-boxes 
should be lined with a wearing- surface of r()U<zli lumber or sheet iron. 
Otherwise the entire box must be replaced when the sides are worn out. 
Board lininfr is easier to place and replace than sheet iron. In early 
Californian practice some of the side lininjis were made of wide, thin 
blocks nailed on so as to present the endjirain to tlie wear. Worn iron 
or steel riffles are used for side lininj; at some places. Usually only the 
lower half or third of the side of the box needs tliis proteetion, and a 
siufrle 2-ineh board may serve not only for lininu- but as a cleat to hold 
down the i-iffles. False bottoms of planed or rou<ih boards may be used 
to save wear on the box proper. 

Each box should rest on three or four sills, efpially spaced. The sills 
and uprifilit nuMubers at the ends of the box serve as battens to prevent 
leakajre at joints. The practice of taperin<r the box enoujrh to permit a 
telescope joint is very convenient in small sluices, especially if the boxes 
must be moved occasionally. Small, three-board boxes may be braced 
with tie>i across the top, although this hampers shoveling: and clean-up 
operations. Larjrer boxes sliould be braced externally from the ends of 
the sills. Sills should be weifihted with rocks to check any tendency of 
the sluice to rise. If the sluice is placed in a bedrock or other cut, water 
under it or at the sides has a stronp: lifting- effect. Moreover, the vibra- 
tion caused by boulders rolling- throu<ih the sluice permits fine prravel to 
be washed under the sills placed on the ground. 

As mentioned, the side lininp: plaid< may serve as a cleat under which 
the riffle sections can be wedged to the bottom of the sluice. Otherw'ise 
some other i)rovision nnist be made as the riffles must be held securely. 
In small boxes it is customary to lay long:, narrow boards on edge on top 
of the riffles and against the sides of the sluice. These boards are 'wedged 
down tightly under cleats nailed i)ermanently to the sides of the box. 
The practice of nailing riffles to the bottom of the box, or using any device 
that recjuires driving luiils in the bottom or sides, should be avoided as it 
results in leaks and eventually damages both sluice and riffles. Wooden 
blocks are the most diflicult to secure in place but can be held by the 
method described in the following section. Rock pavement dejiends on 
its weight, on being packed tightly, antl sometimes on the slight down- 
stream tilt of the individual stones to resist the shifting action of the 
current. 
Maintenance of Sluice-Boxes 

Maintenance work on sluice-boxes consists chiefly in aligning and 
bi-inging to gi-ade any boxes that have moved out of position, replacing 

'" MowU-. A. .1.. Il.\<lr;uili<' niiniiij; in < •:ilif..riiia, lid t<l.. p. 22<i, .Vt-w Vf.rk, Van 
N'o.strand Compuny, 18S!t. 



S( 



T| 



iiydrai'i.k: minixo 



110 



liiiinjis, and plujr<iiii<>' leaks. Attoiition to this work at clean-up time 
will be re])ai(l by {greater (■ai)acity and fi-cedoni fi-oni break-downs when 
the water ajiain is turned into the sluice. 

Size 

As pre\iously shown, sluice-box(>s seldom are built less than 10 inches 
wide for strictly mining pui-poses. Eijrht-inch boxes, liowever, may be 
used in sampiin^' or clcaniufr up. The (piantity of water, with its accom- 
panyinjr load of <:i'avel, that will run tlu'ou«rh a sluice of a p:iven size 
depends upon a number of factors. The practice at the majority of about 
75 hydraulic and jrround-sluice mines visited in the preparation of this 
paper indicates that the carryinji' capacities of sluices of various widths 
are within the followino: limits: 





Width of box, inches 


Miner's inches of water 




From 


To 


12 - . 


25 

100 

200 

500 

1,000 


100 


18 


300 


24 


600 


36 


1 300 


48 to 60 


3 000 







These limits probabh' represent good practice. 

]\Iore trouble is experienced from clogging: of boxes that are too. wide, 
because tlie depth and velocity of water are insui^cient, than from failure 
of boxes to carry their load because they are too narrow. 

The current velocities required to transport different sizes of mate- 
rial have been studied ; works of various authorities are cited by Gilbert." 
The following table is based chiefly on Dubuat's figures for competent 
velocity ; the figures are adjusted to approximate mean velocity instead 
of bed velocity. The last three figures are taken from Van Wagenen."* 



Size of material moved 



Mean velocity, 

approximate feet 

per second 



Sand: 

Fine 

Coarse 

Gravel: 

Fine 

1-inch 

Egg-size 

Boulders: 

3- and 4-inch _ 
6- to 8-inch-. 
12- to 18-inch 



5 
1.0 



15 
4.0 



5.3 

6.7 
10.0 



"Gilbert. G. K., The tran.'^portation of debri.s by running water: U. S. Geol. 
Survey Prof. Paper S(i, p. 216, 1914. 

'2 Van Wagenen, T. F., Manual of hydraulic mining, p. 88, New York, Van Nos- 
trand Company, 1880. '' 



120 I'LACKK MININC. FOK COM) IN (Al.IFORNIA [Bull. 135 

WfllrouiKlcd pebbles are easier to move tlian angular ones, and 
rock of low specific <:ravity' is appreciably easier to wash than heavy, 
dense rock such as <rreenstone or basalt. 

({old ha.s a better opportunity to settle and be cauf?ht in riffles in a 
wide, shallow stream than in a deeper and narrower stream of the same 
volume; the wider sluice, however, usually nnist be set on a steeper grade. 

Small- or medium-size boxes gfenerally are roujrhly square in cross- 
section ; larpre bo.xes iisually are one-half to two-thirds as deep as they are 
wide. The water in a sluice should always be more than deep enough to 
cover the larp-est boulder that may be sent throujrh. In practice, the 
depth of the stream in the main sluice at hydraulic mines usually is a fifth 
to a half the width of the box so as to prevent spills if the box is tempo- 
rarily plufTf^ed by boulders or sand. Where screened prravel is being 
washed, as in undercurrents or on dredges, wude and shallow .streams are 
necessary for the recovery of fine gold. In "booming" operations the 
boxes usually are run full in order to handle the relatively large volumes 
of water that fiow for .short periods only, and the sluices commonly are 
about as deep as they are wide. It would be desirable but impracticable 
to decrease the depth of water by using wider sluices, as flows of 5,000 to 
10,000 miner's inches are not unusual when the gate of the reservoir sud- 
denly is opened wide. 

Grade of Sluice 

Usually the grade of the sluice depends upon the slope and contour 
of the bedrock. If the gradient of bedrock, however, is too low to permit 
sufficient fall for the sluice, cuts or tunnels may be run in the bedrock to 
overcome this difficulty, ^'ery short sluices of only 1 or 2 boxes some- 
times are set nearly flat where there is a drop at the end of the box, the 
gravel being forced through the sluice by the initial velocity and the head 
of water in the pit. 

The opinion of most operators is that about 6 inches in 12 feet is the 
best grade for average conditions. Grades as flat as 3 inches in 16 feet 
can be used but only at great loss of capacity. At the Depot Hill mine, 
where a grade of 3 inches in 14 feet is used, all rocks over 5 to 6 inches 
in diameter must be left in the pit. Because of the greater friction and 
the consequent lowering of velocity, steeper grades are needed for small 
sluices: than for large ones; some operators favor grades of 12 inches to 
12-foot box. For maximum gold-saving efficiency, as well as for economy 
in the dump room, grades should be as flat as possible without lowering 
the velocity to such an extent that the riffles pack with sand. Any 
increa.se in slope from that adjustment will increase the capacity of the 
sluice, increase the wear on the sluice, and decrease the efficiency of the 
riffles, resulting in gold losses if carried to extremes or if the gold is very 
fine. If water is scai'ce. gold recovery may well be sacrificed to capacity. 
Bowie " states that grades of 10 to 24 inches were used in some Forest 
Hill Divide (California) mines for this reason. Increasing the propor- 
tion of water to solids decreases the tendency of riffles to pack with sand. 

Sluice capacity increases with grade but more rapidly ; that is, dou- 
bling the grade of sluice boxes will more than double the quantity of 
gravel that can be put through the boxes by a given flow of water. The 
absolute increase cannot be predicted closely as coarseness of gravel, 

" Bowie, A. .1., A practical treatise on h>draulic mining' in California, 3d ed., p. 220. 
New Yorit. Van Nostrand Company, 1889. 



Sec. T] HYnRAUiiic minino 121 

velocity, and shape of the box appear to have some beariiif? on the relation 
of capacity to slope. F'or instance, Bowie " cites a mine at which chang- 
ing the grade from 8 to 3^ inches in 16 feet increased the quantity of 
gravel sluiced through the same boxes with the same flow of water by 
about one-third. 

The established grade should not be decreased anywhere along a 
sluice, otherwise gravel may accumulate where the current loses velocity. 
If the water and gravel, however, enter the first box with considerable 
speed, say, from the discharge of a hydraulic elevator, the first boxes may 
be placed on less than the regular grade. Bends or curves are undesir- 
able as they complicate construction and induce clogging and running 
over. When a curve is unavoidable it should be as gradual as possible, 
the outside of the sluice should be elevated a fraction of an inch, and the 
grade should be increased perhaps an inch per box at and immediately 
below the curve. Similar rules apply to turn-outs or branches, and drops 
of 3 to 4 inches should be provided at junctions to check the deposition of 
grarel at these points. Such drops occasionally are inserted in straight 
sluices if the grade is available, particularly if the gravel is a difficult 
one to wash or if heavy sand tends to settle to the bottom. A drop of 
even a few inches from one box to the next has a disintegrating effect and 
mixes the material passing through the sluice, thus assisting gold recov- 
ery. At one place where drops were provided at intervals between dif- 
ferent types of riffles, 25 percent of the gold recovered in the sluice was 
found at the drops." 

Theory of Gold-Saving by Riffles 

The function of riffles is to hold back the gold particles that have 
settled to the bottom of a flowing .stream of water and gravel. Any 
' ' dead ' ' space in the bottom of a sluice-box, where there is no current, 
fills quickly with sand and thereupon loses most of its value as a gold 
saver, unless the sand remains loase enough to permit gold to settle into 
it ; therefore, the shape of riffles is important, regardless of the fact that 
under some conditions, as with coarse gold and free-washing gravel, all 
forms of riffles are almost equally efficient. The riffles should be shaped 
so as to agitate the passing current and produce a moderately strong eddy 
or "boil" in the space behind or below^ it, thus preventing sand from 
settling there and at the same time holding the gold from sliding farther 
down the sluice. In other words, riffles, for maximum efficiency, should 
provide a rough bottom that will disturb the even flow of sand and gravel, 
will retain the gold, and will not become packed with sand. Where grade 
is lacking the riffles must be relatively smooth, so as not to retard the 
current unduly ; under these conditions the sluice must be long enough 
to compensate for the loss in gold-saving efficiency of the individual 
riffles. 

Natural stream beds act as gold-saving .sluices, not because they are 
particularly efficient as such but because most gold is "hard to lose" and 
the streams are long. 

"Bowie, A. J., op. cit., p. 266. , ,., ^ „. ,,. ^ ^ • t, • 

isTheller J H, Hydraulicking on the Klamath River: Mm. and Sci. Press, voL 
108, pp. 523-526, March 28, 1914. 



122 



1T.A( KH MIN'INC row fiOI.n IN CAI.IKOHNIA 



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See. I] IlYDHAfMC MIMNC 123 

Types of Riffles 

l\iffl(>s, (if (•(iiirsc, should he designed so ;is lo sjivc llic f^old under tlic 
existiii<r conditions. Tlioy should niso he chcfip, durahh', find easy to 
place and remove. Not all tiies(> (pialities ai'c rounil in any one type. 

Sluice-box i-iffles may ])o classificMl rou<.ildy as transverse, lon<iitu- 
dinal, block, blaidcet. and misccllaneou.s i-ou^hly surfaced ones, oi*. accord- 
ing; to material, as wood block, i)ole, stone, cast iron, rail, an^le ii'on, fab- 
ric, and miscellaneous. Tsually more than one type of liftle is used, 
althou<:li in California very lon^' sluices- have been paved entirely with 
wood-block riffles. 

Of about 80 hydraulic, jii-ound-sluice. and mechanically worked 
placer mines visited in 1!>:^2 by the authors, ajjproximately 25 percent 
used riffles of the transverse variety, loosely termed "llunj^arian," con- 
sistiufj generally of wooden crossbars fixed in a frame and sometimes 
capped with iron sti-aps. About 20 percent used the lonjiitudinal pole 
type, 15 percent wooden blocks, and 15 ])ercent i-ails, the last being 
placed crosswise or lengthwise. Angle-iron riffles, wire-mesh screen or 
expanded metal on carpet, blankets, or burlaj), rock paving, and cast-iron 
sections together made uji the i-emaining 25 percent. The oidy general 
rule observed was that the size of the riffles was roughly proportional to 
the size of the material to be handled and that for fine material, particu- 
larly the screened gi-avel washed in most of the mechanically operated 
plants, the di-edge-type riffle found most favoi-. 

For a small or medium-size sluice (if luiidjer is costly and a plentiful 
supply of small timber, such as the lodge-pole pine so connnon in many 
Western States, is available) peeled pole riffles are perhaps the most eco- 
nomical and satisfactory of the various types. Those of transverse vari- 
ety may have a somewhat higher gold-saving efficiency, but undoubtedly 
they retard the current more and wear out faster. Poles 2 to 6 inches in 
diameter may be used, spaced 1 or 2 inches apart. Such i-iffles are cheap 
but wear out rapidly. The sections should be a third or half the box 
length for convenience and 1 or 2 inches narrower than the sluice. At 
the Golden Rule mine 6-inch pole riffles had to be replaced every 10 days 
or after each 1.200 cubic yards had been sluiced. The sluice was 30 
inches wide and had a grade of 8 inches in 12 feet. At other mines poles 
last several times as long. 

If sawed lumber can be obtained cheaply, riffles similar to the one 
de.scribed may be made of 1- by 2-, 2- by 2-, or 2- by 4-inch material. The 
top surfaces of the riffles may be plated with strap iron. Transverse 
riffles of this type may be slanted downstream and the top surfaces may 
be beveled to increase the "boiling" action, as with the dredge riffles. 
The effectiveness of this practice is not known, and the authors know of 
no conclusive tests having been made. Longitudinal riffles of 2- by 4-, 
3- by 4-, or 2- by 6-inch material are used at some ])Iaces. 

Wooden-block riffles are held by P.owie'*' to be unexcelled in regions 
where the material is available cheap. The blocks are 4 to 12 inches 
thick and of corresponding diameters or widths. They may be round, 
partly squared, or cut from square timber. One- or two-inch wooden 
strips separate the rows of blocks, and they are held securely in place by 
nails driven in both directions. "Wooden-block riffles are perhajjs the 
hardest of all types to set because of their tendency to float away. They 

i« Bowie, A. J., op. cit., p. 225. 



124 PLAf'KR MININ'O FOR OOLD IN CAI.IFORNIA [Rull. 135 

must be nailed to the spaeinjr strips, as stated, and \vedpred seenrely at 
the sides. The spaeiii}; strips are held down at either end by the side 
linint; of the sluice. Wooden-bloek riffles are durable, ean be worn down 
to half their ori^'inal thickness or less, and if made of lonjr-frrained wood 
(such as pitch pine, which "broom?." instead of wearing; smooth) may 
catdi .some jrold in the end^'rain. When discarded, they arc commonly 
burned and the ashes panned to recover any «rold so caujrht. The life 
of 10- or r2-inch wooden-blo'-k riffles may be a few months to several sea- 
sons and, aecordinfr to Bowie, ranfjes from 10(),0()() to 2()(),00() miner's 
inches of water; that is, with a flow of 1,000 inches one would last 100 to 
200 days. The grade of the sluice apparently has much to do with the 
life of block riffles. At the Superior min'^ where the sluice was 48 inches 
wide and had a grade of 21 inches in 12 feet a set of blocks lasted two sea- 
sons, during which time 140,000 cubic yards was sluiced. At the Salmon 
River mine the grade was 7 inches in 12 feet and the width of the boxes .30 
inches. Here block riffles la.sted 60 to 70 days, during which time about 
18.000 cubic yards was washed. On account of differences in the wear- 
ing rates only one variety of wood should be used in a section of a sluice, 
Douglas fir wears longer than other native western conifers. 

Stone riffles are durable and fair gold catchers. Stones ranging 
from the size of cobbles to 8 or 10 inches in diameter are packed closely 
on the bottom of the sluice. They may be held at intervals of a few feet 
by transverse wooden strips. In some instances the stones are roughly 
hand-shaped and set similarly to street paving. Stone riffles are difficult 
to set and generally are not used in portions of a sluice that are cleaned 
up frequently. Their main advantage is their long life. Because of 
their roughness, stone riffles require a steeper slope than wood blocks, a 
feature that sometimes would prohibit their use. 

Where large quantities of gravel are put through sluices, iron or 
steel riffles generally are preferred. Their superior wearing quality as 
compared with that of wood permits longer runs without stopping to 
replace the riffles. Their durability may more than compensate for their 
higher cost. 

Steel rails and angle iron are common riffle materials used in various 
ways. Old rails or angle iron can often be obtained cheaply in mining 
districts or near railroads. Various other steel products such as pipe and 
channels have been utilized for riffles. Cast iron is also used and has 
the advantage of a lower first cosi than steel rail or angle iron. 

Iron or steel riffles should not be used in units too long to be handled 
readily. Rope blocks on movable tripods have found favor at some places 
for lifting heavy riffle sections. 

When used as transverse riffles lengths of steel rail usually are set 
upright, the flanges almost touching or not more than 1 or 2 inches apart. 
Where grade is lacking and gold saving is not particularly difficult, longi- 
tudinal rail riffles make excellent paving for a sluice as they provide a 
smooth-sliding bottom for the gravel and boulders. The rails ordinarily 
are bolted together by tierods passing through wood, pipe, or cast-iron 
spacing blocks, forming riffle sections the width of the sluice and any con- 
venient length. At La Grange mine in Trinity County, California, 40- 
pound rails costing about $125 per ton proved more satisfactory than 
wood riffles.'^ W^hen 16- by 16- by 13-inch wood blocks were used the 

"MacDojnald. D. F., op. clt. 



Sec. I] HYDRAULIC MINING 125 

riffles tended to "sand up." Moreover, the blocks had to be replaced 
every 2 or 3 weeks. Leno:th\vise rails 8 inches apart lasted 2 months 
and rails 5 inches apart, 4 months. Strangely enough, transverse rails 5 
inches apart lasted 6 months. The rails were spaced by cast-iron lugs 
and set right side up on timber sills. When the head of the rail was worn 
off the remainder was used for side lining. This sluice was handling a 
flow of about 4,000 inches of water and 1,000 cubic yards of material per 
hour, boulders as large as 7 tons being washed through. The eddies 
behind the rails were believed to be the cause of the improved recovery 
as compared with that using block riffles. The lower part of the branch- 
ing sluice line was cleaned up every other season only. The combina- 
tion of steel rails and wooden sills used at La Grange mine appears to 
make an excellent gold saver, and modifications have been used at many 
large mines. 

Angle iron is commonly used for making riffles. Many methods of 
assembling the lengths of angle iron into riffle sections are in use, and no 
one method can be said to excel. The irons may be set with flat upper 
surfaces or inclined slightly to increase the riffling action. Usually the 
gap between the riffle bars is ^ to 1 inch. The effectiveness of this type 
of riffle is believed by some operators to depend largely on the vibration of 
the riffles under the impact of boulders, which keeps the sand trapped 
under the angles in a loose condition favorable to gold saving. 

Cast-iron riffles of all shapes and sizes have been used. If available 
at low cost they are very economical, as they wear slowly, can be quickly 
and securely placed, and are efficient gold savers if designed so as not to 
pack with sand. In an undercurrent at the Indian Hill mine, California, 
cast-iron riffles were in use that were 4 feet long, shaped like angle irons, 
and had equal 3|-inch legs -| inch thick. 

For shallow sluice streams carrying only fine material various gold- 
saving materials are used, including brussels carpet, coco matting, cor- 
duroy, and burlap. These may be held down by cleats or by wire screen. 
Fabrics often are used in combination with riffles to catch fine gold and 
hinder its being washed out of the riffles by eddies. A corduroy woven 
specially for a riffle surface is used by some large Canadian lode-gold 
mines to catch their "coarse" gold before flotation or cyanidation. As 
such gold would be considered fine by most placer miners it seems prob- 
able that such a fabric would be useful for treating finely screened placer 
sands. The corduroy in question has piles about ^ inch wide and ^ inch 
high, spaced about \ inch apart. The piles are beveled slightly on one 
side. The cost in Canada is about $1.00 per square yard. 

Heavy wire screen such as that used for screening gravel makes an 
excellent riffle for fine or medium-size gravel in fairly shallow sluice 
streams, and generally it is used with burlap or other fabric underneath. 

Expanded metal lathing and woven metal matting are common types 
of riffles for fine material and are used with carpet or burlap. If the thin 
strands of metal slant considerably in one direction, the material should 
be placed with this direction downstream. Eddies in back of the strands 
will then form gold catchers, whereas if the recesses face upstream they 
will at once fill with a tight bed of sand and lose their effectiveness. 

Solid-rubber riffles were noted at one washing plant. Sponge-rubber 
riffle material is on the market, but it was not observed in use and nothing 
is known by the authors of its merits or cost. 



126 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull, lo") 




Kin. -M. LMokniK down ff.iii hillsulc ;U sluic- and 
undercurrents. Lower end of sluiie is in center t)f photo. 
Reprinted from California Journal of Mines and Genlofjjj, 
January I'Jil, p. 61. 



Sec. I] IIYDHAULIC MININO 127 

Anotlier form of riffle often used as An auxiliary to otlier types is a 
mercury trap, consisting of a board the full width of tlie sluice with 1- 
or li-inch auj>er lioles in which mercury is placed. Instead of round 
lioles, transverse }i:r()oves or lialf-moon-sluiped depressions, 2 to 4 indies 
wide and with tiie rouiuled, deep side downstream, may be cut in a wide 
board and partly filled with mercury. These riffles have no apparent 
advantage over tlie ordiiuiry transverse-bar type and ai-e suitable only for 
fine gravel, as lai-ge pebbles would sj)lash the mercury out of the traps. 

Many ingenious and odd kinds of riffles ai'c encountered in the field, 
some of which have been i)atente(l. It is veiy uidikely, however, that 
the advantage of any unusual oi- freakish design of i-iffle is sufficient to 
offset the cost of I'oyalties on patented inventions. 

Undercurrents 

An undercurrent, as dcfiiu'd before, is a device for sluicing sepa- 
rately a finer part of the gravel ])assing through the nuiin sluice. The 
fine material and a i-egulatcd (luantity of watei- i)ass through a stationary 
grizzly in the bottom and usually near the end of the sluice to one or 
more wide sluice-boxes, connnoidy called tables, paved with suitable 
riffles. If the main sluice is in sections, with drops between, the water 
and sand may be returned from the undercurrent tables to the main 
stream, and several undercurrents may be installed at convenient points 
along a sluice. 

The sci-een or grizzly in the main sluice may present the most diffi- 
cult problem in building a satisfactory undercurrent. The screen should 
divert all the undersize yet not take so much water that it causes plugging 
of the main .sluice below the undercurrent. The proper size of opening 
can be determined oidy by experiment. A screened or barred opening, 
tiie full width of the main sluice and a few inches to a foot or more long, 
will usually draw off as much water as can be spared. New water may 
be added to either the undercurrent or main sluice if the screen opening 
does not take out the right (piantity for successful operation. Usually 
minus ^- to l-inch material is desired for the undercurrent, and either 
punched-plate screen or iron-bar gi-izzlies may be used to make the separa- 
tion. Grizzlies should be made of tapered bars or screens i)unched with 
tapered holes with the largest openings downward, otherwise they will 
plug and render the undercurrent iiieffective. 

Because undercurrents need a wide, shallow .stream, grades of 12 to 
18 inches per 12 feet must be used, depending largely on the type of riffle. 
Cobblestone, block, tran.sverse or longitudinal wooden strips, rails, 
screens, or fabrics may be used for riffles. Often several types of riffles 
are used on successive parts of one undercurrent. Undercurrents may 
be a few to 25 or 30 feet wide and 10 to ;")() feet long 

Most of the gold recovered by undercurrents is so fine that it does 
not settle in the relatively swift, deep current of the main sluice, but 
part consists of gold that is freed from its matrix of clay by dropping 
through the grizzly and rolling over the uiulercurrent riffles. All coarse 
gold is saved in the first few boxes of the main sluice \ndess conditions 
are radically wrong. Unless the undercurrent is installed at the end 
of the sluice, or at least below where gold is recovered, not all the saving 
in the undercurrent .should be credited to its installation. In the early 
daA's when hydraulicking Avas at its height undercurrents were much 
favored, sometimes 5,000 to 10,000 square feet of undercurrent being used 



128 placp:r minino for oold in California [Bull. 135 

along a single sluice line. The gold saved in them occasionally exceeded 
10 percent of the total clean-up but more often was less than 5 percent. 
As this recovery usually was effected by 5 or 10 large tables and as con- 
siderable would have been saved by the main sluice without the under- 
currents, the economy resulting from their use was perhaps doubtful. 
Bowie'® presents details of the use of undercurrents in early Californian 
practice and indicates that their particular field lay in the treatment of 
cement gravels. Of the several undercurrents observed by the authors 
in use in 1932 it is doubtful if many were justifying their installation. 

Operation of Sluice- Boxes 

Under favorable conditions a properly designed and constructed 
sluice-box requires little attention other than periodic clean-ups and 
nrinor repairs which are made at the same time. Unfortunately, such 
a combination rarely occurs, and an appreciable part of the miner's 
operating expense is chargeable to work along the sluice lines. 

The best results are obtained when a steady flow of water and gravel 
passes through the sluice. An excessive flow of clear water through the 
sluice will bare the riffles, causing some gold to be lost. On the other 
hand, a continued overload of gravel will plug the sluice at some point 
so that sluicing must be stopped for the time needed to clear the obstruc- 
tion ; this time lost may be appreciable. If plugging can not be prevented 
by increasing the grade or the flow of water or reducing the feed, one or 
more sluice tenders must work along the sluice with forks or shovels to 
keep it open. This added cost may be serious at small mines. All effort 
should be directed toward getting the gravel into the box and letting the 
water do the rest. 

Large boulders are another cause of expense and lost time. "When 
the maximum size of boulder that the sluice will carry is known, all 
boulders larger than this should be prevented from entering the boxes. 
Relatively little work directed to this end will save hours of delay in 
clearing plugged sluices and unnecessary wear and tear on the boxes 
and riffles. 

An exception is found in the operation of "booming." A necessary 
condition of this work is a heavy head of water which usuallr fills the 
sluice to the brim. Sometimes little or no work can be done in the pit 
while the water is on, and the entire crew may profitably patrol the sluice 
with long-handled shovels to guard against stoppages which might be 
disastrous becau.se of the large flow of water and gravel. Before each 
"boom" all oversize boulders should be moved out of the course of the 
water. 

Cleaning Up 

Clean-up time should be kept to a minimum. This can be done by 
cleaning up as seldom as practicable and by using efficient methods. 
Large hydraulic mines, particularly if the water season is short, clean 
up only once a season except perhaps the upper one or two boxes. Dredges 
clean up every 10 days or 2 weeks, because large amounts of gold are 
recovered in relatively short sluices with attendant possible loss when the 
upper riffles become heavily charged. This necessary delay is used for 
routine repairs on the dredge. In ground-sluicing the clean-up period 
ranges from weeks to months, while in shoveling-in operations the sluice 

"Bowie, A. J., op. clt., pp. 252-262. 



Sec. I] HYDRAULIC MINING 129 

may be partially cleaned up daily. The danger of theft from the upper, 
richer boxes can be lessened by filling them with gravel at the end of 
each day's work. 

The general principle is the same in all clean-up operations, but 
practice differs widel}'. Clear water is run through the sluice until the 
riffles are bare, the stream being reduced enough to prevent washing out 
the gold. Then the water is turned off or reduced to a very small flow, 
and the riffles of the first box are lifted, washed carefully into the box, 
and set aside. Any burlap or other fabrie used under the riffles likewise 
is taken up, rinsed into the box, or placed in a tub of water where it can 
be thoroughly scrubbed. Then the contents of the sluice are shoveled to 
the head of the box and "streamed down" with a light flow of water. 
The light sand is washed away, and rocks and pebbles are forked out by 
hand. This operation is repeated until the concentrates are reduced 
to the desired degree of richness. Gold or amalgam may be scooped up, 
as it lags behind the lightest material at this stage, or all the black sand 
with the gold, mercury, and amalgam may be removed and set aside for 
further treatment. Successive boxes are treated similarly, until the sluice 
is bare. The last step is to work over the whole sluice with brushes and 
scrapers to recover gold and amalgam caught in cracks, nail holes, or 
corners. At the Wisconsin mine a small box was set up in the main sluice 
and the concentrate from the riffles shoveled into it to reduce the bulk. 
At the Round Mountain mine the concentrate from the lower section of 
the sluice was treated in a quartz mill. 

Use of Quicksilver in Sluicing 

Quicksilver is used at nearly all placer mines. If it is not used to 
catch gold in the sluices at least it is probably used in extracting the 
gold from the concentrates. The average market price for mercury in 
1932 was about $58 per 76-pound flask, but quicksilver purchased in 5- 
or 10-pound lots from a chemical-supply house cost about $1 per pound. 
Except in districts where placer mining was particularly active, drug 
stores or other local retailers charged about double this amount. The 
price in January 1934 was $67.54 per flask, and in late 1945 was $106 
per flask. 

The characteristics of quicksilver that make it of value to the miner 
are: (1) Its power of amalgamating with gold and silver; (2) its high 
specific gravit}' (13.5), which causes it to lie safely under a stream of 
water and gravel, floating off on its surface everything but the native 
metals ; and (3) its relatively low boiling point (about 675° F.) far below 
red heat, which allows it to be driven off by heat from the gold with which 
it has amalgamated. 

Amalgamation is a process in which mercury alloys with another 
metal. All metals but iron and platinum amalgamate more or less readily. 
Clean and coarse placer gold alloys readily, but if the gold is partly coated 
with iron oxide or other substances (for example, "rusty" gold) it amal- 
gamates Avith difficulty. The mercury itself should be clean enough to 
present a smooth, shiny surface ; the presence of some gold or silver in 
the quicksilver, however, is said to facilitate amalgamation, that is, to 
make it more "active." 

Quicksilver is placed carefully in the sluice-boxes, where it finds its 
way to the many recesses in the riffles and lies in scattered pools, ready 
to seize and hold any particle of gold that touches it. It is used in this 

9 — 56968 



130 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 135 

manner in almost all important liydraulic operations, but some operators 
place it in the boxes only shortly before the clean-up, evidently believing 
that the added gold saved by its use during sluicing does not compensate 
for the loss of the mercury that passes through the sluice with the tailings 
or escapes through cracks or other leaks. In exceptional instances the 
conditions are such that the mercury ' ' flours, ' ' that is, breaks into minute, 
dull-coated drops. Flouring is aggravated by agitation or exposure of 
the mercury to air. The common practice of "sprinkling" it into sluice 
boxes may be condemned on this ground, as well as for the reason given 
by Bowie*" that the fine particles formed by careless sprinkling are more 
readily washed away and lost. F'louring is responsible for the most 
serious losses of quicksilver with the tailings. 

Even under the best conditions, 5 to 10 percent of the mercury used 
is lost. If steep grades, heavy gravel with consequent severe pounding 
and vibration, old and leaky sluices, or other adverse conditions exist, 
the loss of mercury may be 20 or 25 percent. 

Only clean mercuO' should be placed in a sluice; even this tends to 
become fouled or sluggish and to lose its effectiveness. The best cleansing 
process is retorting, which is discussed later. However, straining the 
mercury through chamois or tightly woven cloth removes some of the 
surface scum and foreign material, or the mercury may be treated with 
potassium cyanide or other chemicals to dissolve the impurities. It 
should be handled as little as possible and kept from contact with grease 
or other organic material. 

Wilson-" suggests a cow's horn, sawed off near the small end to 
leave a hole that can be stopped with the finger, as a useful implement 
for charging sluices. Most miners charge the sluice from stoneware or 
heavy glass bottles such as are used for champagne. 

Mercury should be kept or carried only in iron, glass, or earthenware 
containers because of its tendency to amalgamate with zinc (galvanized 
iron), tin, or other metals. 

The quantity of ([uicksilver used differs according to conditions and 
custom. According to Bowie,-' 200 or 300 feet of 6-foot sluice should 
receive about three flasks (225 pounds) as a first charge and a 24-foot 
square undercurrent, 80 or 90 pounds. At the Depot Hill mine one flask 
is placed in the first four or five boxes each month during the washing 
season. At another mine two flasks were used in a season during which 
100,000 cubic yards was washed. Dredge tables, with areas of 1,000 to 
10,000 square feet, are charged with 150 to 3,000 pounds of mercury. 
According to Janin,-- a 7-foot dredge with a table area of 2,800 square 
feet uses about 1,000 pounds on the sluices and in the traps. Probably 
in common practice the range is ^ to i pound per square foot of sluice 
area. 

The sluice should be run long enough to plug all leaks before the 
mercury is added. Usually only the upper 2 or 3 boxes or a quarter or 
half of the sluice at most is charged with mercury, as otherwise consider- 
able loss occurs. During a run more mercury is added periodically. 

'•Bowie, A. J., op. cit., p. 244. 

»" Wil.son. E. B., Hydraulic and placer mining, 3d ed., p. 230, John ".VUey & Sons, 

=" Bowie. A. J., op. cit., p. 244. 

"Janin. Charles, Gold dredging in the United States: U. S. Bur. Mines Bull. 127, 
p. 143. 1918. 



SOC. I] lIYl)KAri,I( MINIXG 131 

AVhenever the sluice is run down enoufjh to expose the riffles the mercury 
can be examined. If it does not show here and there with clean surfaces 
nearly to the top of the riffles, more is added. As the quicksilver takes 
up gold near the head of the sluice it becomes pasty and finally quite 
hard and more should be added to keep it in a fluid condition. 

The use of mercury in recovering gold from sluice-box concentrates 
is discussed in the following section. 

Amalgamating plates should be u.sed only in treating fine material, 
generally well under one fourth inch in size and preferably not coarser 
than lO-mesh, as larger particles abrade the plates too rapidly and pre- 
vent building up of the amalgam. Consequently, the application of 
plates to placer mining is limited to the stamp milling of some drift-mine 
gravels and the treating of fine undere-urrent or other screened sands. 
The use of plates in stamp milling is a phase of metallurgy beyond the 
scope of this paper, and reference is made to any standard text or hand- 
book on gold milling. 2^ 

None of the other applications of amalgam plates to placer raining 
is of particular importance, probably because the recoveries seldom have 
justified the labor and expense. Plates may be set in undercurrents 
treating finely screened sands, such as beach sands or the Snake River 
gold-bearing sands. They usually are covered with burlap to assist in 
retaining the gold until it has come in contact with the amalgam. Many 
other amalgamating devices have been applied to such material, but 
none is known to the authors to have been of greater value than properly 
designed sluices and riffles. 

Separation of Gold and Platinum-Group Metals From Concentrates 
General 

No sluice box or other type of gold saver used in large-scale placer 
mining makes a clean separation of the valuable minerals. The concen- 
trate obtained must be treated further to make a marketable product. 
Concentrate obtained in cleaning bedrock in some types of mining is 
treated similarly to sluice-box concentrates. 

The concentrate may be cleaned by panning or rocking in auxiliary 
sluices or by blowing, or it may be amalgamated in a special type of appa- 
ratus. The treatment will depend mainly upon the scale of operations, 
the proportion of black sand in the concentrate, and the characteristics 
of the gold. The general methods of cleaning concentrate with pans, 
rockers, or small sluices are the same as those in small-scale mining, 
described in a previous paper,-^ except that more care is required and 
smaller quantities are treated at one time. In treating small quantities 
of concentrate, however, it should be remembered that colors of gold so 
fine as to present great difficulty in their separation by panning or rock- 
ing are probably of small value, and their loss would be inconsequential. 

If precise results are desired for sampling or testing, the concen- 
trates should be amalgamated. 

23 See also Chapman, T. G., Treating gold ores: Arizona Bur. Mines Bull. 133, 
Univ. Arizona, 1932 ; a brief, nontechnical description of the methods of treating gold 
ores. 

2« Gardner E. D., and Johnson, C. H., Placer mining in the western United States, 
general, hand-mining, and ground-sluicing : U. S. Bur. Mines Inf. Circ. 6786, pt. 1, 
73 pp., 1934. 



132 PLACF.R MINING FOR OOLD IK CALIFORNIA [Bull.135 

Panning 

Panninf? is the simplest method of separating the valuable constitu- 
ents from the worthless material and generally is used in small-scale 
operation. The method, however, is tedious if the gold is very fine and 
the concentrate contains much black sand. Mercury may then be used 
in the pan to collect the gold. 

Rocking 

Larger quantities of concentrate may be treated in a rocker and the 
resulting .semifinal product cleaned further in a pan. A final or almost 
final product, however, can be made in a rocker, the flat, smooth bottom 
of which, set on a gentle grade with screen and canvas baffle removed, 
offers an ideal surface for the purpose. 

The concentrates are placed at the upper end, and a small stream of 
water is poured over the .sand while the rocker is swayed gently back and 
forth. The lighter material is washed down to the riffle at the lower end, 
and the coarser particles of gold are left behind. These are picked up 
with a scraper, and the operation is repeated, a portion of the concen- 
trates presently being discarded with each washing until at length all 
gold of appreciable value has been recovered. This method is satisfac- 
tory with ordinary concentrates, but if the gold is very fine, flaky, or par- 
ticularly light, porous, or angular, the .separation is tedious and unsatis- 
factory, and amalgamation is to be preferred. 

The same general method may be used in the mine sluice to recover 
the bulk of the gold amalgam. 

Auxiliary Sluices 

Sometimes an auxiliary sluice is used to reduce the volume of con- 
centrate from the mine sluice or to treat concentrate after it is amalga- 
mated. The small sluice in turn must be cleaned up. At one mine a 
12-inch box was set up in the main sluice into which was shoveled the 
riffle concentrate from below. 

Blowing 

The grains of sand remaining in an almost final product may be 
removed from the gold by blowing. A flat metal or paper sheet, such aa 
a piece of drawing paper or a large flat tin about 2 feet square with the 
edges bent up about one-half inch, is best for the purpose. However, 
with care ami skill the operation can be performed in a common gold pan, 
as is done by many prospectors, particularly when cleaning dry-washer 
concentrates. The material should be perfectly dry. Much effort is 
saved by using a magnet to take out any magnetite sand in the concen- 
trates; often this mineral comprises as much as 90 percent of the mate- 
rial. A piece of paper folded around or held against the end of the mag- 
net will keep the magnetite from sticking to the metal. When all the 
magnetite is removed, blowing gently on the remaining sand and gold 
will drive the former to the farther edge of the sheet, leaving the gold 
behind. In mo.st instances the loss of a few fine colors is not serious. 

An^algamation 

In Ordinary GoUt Pans. A small (pumtity of quicksilver, ranging 
from an ounce to a quarter of a teaspoonful, will catch all the gold from 
a pan of sluice concentrates. The mercury is simply placed in the pan 
with about T) pounds of concentrates and agitated under water until no 



Sec. I] HYDRAULIC MINING 133 

more free gold can be observed. Then the sands are panned off, care 
being taken not to lose any of the amalgam or fine drops of mercury, 
which gradually will run together into a single mass. If the concentrates 
are nearly all black sand only a small quantity should be washed at a time, 
but if much light sand or rock is present larger (}uantities can be washed. 
Copper-plated pans or pans with steel rims and copper bottoms are 
available and are useful for saving fine gold in concentrates. The copper 
is coated with mercury by first cleaning it with emery paper, then rub- 
bing clean, bright mercury or amalgam on it until it presents a smooth, 
shiny surface. The gold in the material being treated is picked up 
quickly by the amalgam surface. Only fine sand can be treated to advan- 
tage as coarse sand or gravel will scour the amalgam off the copper. As 
fast as amalgam accumulates on the copper it is scraped off with a smooth, 
dull-edged iron scraper such as a putty knife. More mercury may then 
be added to keep the surface bright and in a "receptive" condition. 

Amalgamators. In nearly all large-scale operations most of the gold 
is amalgamated in the sluice boxes or on the riffle tables, and the amalgam 
is separated from the sands during clean-up operations or from the con- 
centrates by rocking or panning. Tarnished or rusty gold or very fine 
gold, however, does not amalgamate readily because it is difficult to make 
contact between the gold and quicksilver. Such gold, generally included 
in a black-sand concentrate, requires agitation in the presence of quick- 
siWer or, if rusty, grinding to remove the interfering coat for satisfactory 
amalgamation. 

Mechanical amalgamators are used to treat such materials. Occa- 
sionally all of the concentrate from the sluice will be treated in an amal- 
gamator, particularly if it contains rusty gold. The charges for the 
amalgamator should be kept clean ; grease especially interferes with amal- 
gamation. 

A common type of amalgamator is the clean-up pan, which consists 
of a cast-iron, cylindrical, flat-bottomed barrel or tub 1 or 2 feet in diam- 
eter for small-scale work and 4 to 6 feet in diameter for mill service. The 
concentrate with 1 or 2 percent quicksilver by weight is placed in the pan 
with suiflcient water to make the mass fluid and agitated by a revolving 
spider. The quantity of water added should be sufficient only to permit 
agitation without too great strain on the machine. The pulp should be 
thick enough to hold particles of mercury in suspension. Shoes on the 
lower end of the spider arms slide on a flat, circular race in the bottom of 
the barrel, thus adding some grinding to the agitation. After running 
for 1 or 2 hours the batch may be emptied through a drain plug in the 
bottom of the barrel and the mercury and amalgam separated from the 
sand by panning. Some pans are provided with side drain plugs at vari- 
ous elevations. The rotation may then be slowed from its usual speed of 
about 60 r.p.m., the shoes raised enough to stop the grinding, and water 
added. This will settle the quicksilver and amalgam ; the waste sludge 
can then be flushed out through the upper drain plugs and almost com- 
plete cleaning of the amalgam and mercury made in the pan itself. 

Another device, the so-called amalgam barrel, generally is used at 
large stamp mills and occasionally is employed in placer operations, par- 
ticularly in dredging, to treat accumulated black sands, scrap metal, and 
other possible gold-bearing material from clean-up operations. It is 
merely a cast-iron or steel drum revolving on a horizontal axis like a ball 



134 I'LACER .MININfi FOR (iOLD IN CALIFORNIA [Bull.135 

mill and fittetl with suitable drain plugs, handholes, inanlioles, or remov- 
able ends, depending on its size and use. The material to be treated is 
l)iaoed in the barn^l with quicksilver, water, and a few iron balls, and the 
barrel is turned slowly for an hour or several hours. The barrel may 
then be flushed with water from a ho.se to wash away the lighter products 
of grinding, turiu'd ovei'. and emptied into a tub, the amalgam and mer- 
cury being recovered by jianning. Potassium cyanide .sometimes is added 
to brighten the gohl ; oidy enough is used to make a very weak solution. 

An amalgamator that occasionally is used, especially if a part of the 
gold is attached to particles of (piartz, is the Herdan pan, which is rela- 
tively simple in construction and cheap to operate. The pan consists of 
a revolving cast-iron bowl, usually .'5 to 5 feet in diameter, with a raised 
central hub for the drive shaft, giving it the form of a circular trough. 
The bowl is supported either by the drive shaft or by rollers and is set 
with a tilt of about 20 or :}()° from the horizontal. It is driven at 10 to 
•iO r.p.m. cither by a crown gear on the inclined shaft of the bowl or by a 
ring gear on the bottom of the bowl. One or two large cast-iron balls roll 
in the trough as the bowl revolves. Quicksilver is placed in the bowl with 
the charge, and as the device revolves a stream of water is directed into 
it and overflows at the lowest point of the rim. The material to be amal- 
gamated may be added in batches or, if it is to be ground as well as amal- 
gamated, by an automatic feeder, the slimes and fine material overflowing 
to waste; the bowl then acts as a classifier. For placer concentrates the 
batch process is used, 100 pounds or more being treated at a time. Too 
large a quantity of .sand lessens the grinding effect of the balls. 

A 1- or 2-cu.ft. hand- or power-driven concrete mixer is a convenient 
amalgamating device for the small- to medium-scale placer miner, par- 
ticularly if part of the gold is rusty. It co.sts only $20 to $30, excluding 
the small gasoline engine, and can be obtained from hardware stores or 
mail-order houses. The charge for such a machine is two or three pails 
of concentrates, 1 or 2 pounds of quicksilver, a few round cobblestones 
3 or 4 inches in diameter, and water. About a 1-hour treatment will 
amalgamate practically all of the gold. The charge is emptied into a 
settling tub and then washed in a pan or small sluice box to recover the 
amalgam and mercury. 

Regardless of the amalgamator used, too violent agitation of the mer- 
cury must be avoided, otherwise excessive flouring hinders amalgamation 
and makes it difficult or impossible to recover the quicksilver. 

Cleaning A maUjam. The mixture of quicksilver and amalgam from 
sluice-box clean-ups u.sually contains much more mercury than amalgam. 
It can be freed from sand, scraps of iron, and other .solid impurities by 
careful panning and by washing with a jet of clean water. The amalgam 
can then be .separated from the quicksilver by straining the mixture 
through buckskin, chamois skin, close-woven canvas, or other .strong, tight 
cloth. This generally is done by hand, preferably under water to pre- 
vent scattering of the mercury. The quicksilver tlius filtered off contains 
at the most only about one-tenth percent of gold; this mercury is desir- 
able for recharging the boxes as the .small amount of gold makes it more 
active. The amalgam, after squeezing, still contains some mercury, part 
of which may drain off if the mass is suspended for several hours in a 
funnel or other similar container. With or without this last refinement, 
which one dredge operator used with success, the stiff, pasty amalgam is 



Soc. T] HYDRAUIilC MIMN'G 135 

now ready for fire treatment to separate the gold. It eontaiiis 25 to 55 
percent, eoninionly about a tliird by weiprlit of {?old and silver. 

Extracting Gold From Amalgam 
Heating 

Altli()U<rh i-etortinp: is tlie comiiion inetluul of separatinpr the gold 
from the (|uicksilvei- in amalfram at dredf^'cs and other larpre-scale opera- 
tions, the merenry in small <|uaiitities of amal<:<im may be volatilized by 
simple heatinjr. A common method is to heat the amalgam on a clean 
iron surface over an open fire or for<re, or in a furnace, until all the mer- 
cury is driven off. This is the usual expedient of the single miner or 
small operator who does not object to the loss of the small quantity of 
([uicksilver involved. The mcrcui-y vapor may appear as heavy white 
fumes. Whether visible oi- not, mercury vapor is exceedingly poisonous, 
and the work must not be done except where a draft can be depended on 
to carry all the vajior away from the operator. As stated elsewhere, mer- 
cury boils at 675"^ F., a temperature about halfway betAveen the boiling 
point of water and the first visible red heat of iron. However, it volatil- 
izes at the boiling point of water enough to be dangerous to the health of 
persons exposed to it. Conse(|uently, it should be handled carefully, 
particnlarly to avoid iidialing its vapors. 

In another method of recovering the gold from small amounts of 
amalgam, a potato is used as a condenser. This is a device popular with 
prospectors because it is very simple, yet saves part of the mercury that 
would be lost by the method previously described. A large potato is cut 
smoothly in half, and in the flat surface of one-half a recess is hollowed 
which .should be considerably larger than the amount of amalgam to be 
treated. The amalgam is placed on a clean sheet-iron surface, the half 
potato is placed over it, and the whole is set over a hot fire. For conven- 
ience it may be done in a frying pan or the scrap of sheet iron put on a 
flat shovel so that it can be withdrawn readily from the fire. Some mer- 
cury vapor will escape under the edges of the potato, and, as before, these 
fumes must be avoided. After 15 or 20 minutes of strong heating the 
potato may be lifted oflP for inspection. If all the mercury is gone from 
the gold the potato may be crushed and panned, and a considerable part 
of the mercury will be recovered. It may be desirable to heat the gold 
further to ainieal it ; this can be done without removing it from the iron 
plate. Any tinned or galvanized metal intended for use in this process 
should be heated redhot and then scoured to remove all traces of the coat- 
ing so that a clean iron surface will be presented. 

A laboratory method of separating the gold is to put the amalgam 
in a small beaker and di.ssolve the mercury in a 1 to 1 solution of nitric 
acid and water. When all the mercui-y is dissolved, the gold may remain 
as a sponge, which can be washed gently in water and annealed in a small 
porcelain crucible. More frequently the gold Avill be recovered as a fine 
dust, which also can be washed and annealed but is less easy to handle. 

Retorting 

A very small amount of amalgam can be retorted quickly and easily 
in a laboratory in a gla.ss tube 18 to 24 inches long, sealed at one end and 
bent 2 or 3 inches from that end to a slightly acute angle. A large tube 
three-fourths inch in diameter is best. The amalgam is broken into 
pieces small enough to be dropped into the closed end where it is then 



136 PLACER MININfi FOR GOLD IN CALIFORNIA [Bull. 135 

heated, tlie fumes condensing in the long open end of the tube. The gold 
can be annealed by heating the tube to redness after all mercury is 
driven off. 

A retort for treating a few ounces at a time can be made cheaply of 
ij-inc'h pipe, pipe connections, and a large grease cup. The lower and 
open end of the ij-inch pipe is inclo-sed in a larger pipe. Cooling water 
i.s poured through the space between the two pipes from an open connec- 
tion in the top of the outer one. The charge of amalgam is i)laced in the 
grease cup cover which is then screwed into place; graphite lubricant is 
placed on the threads to make a tight joint. Heat is applied to the grease 
cup, and the (piicksilver is condensed in the lower end of the pipe. The 
method of using and the general arrangement of the device are similar 
to those of tlie next retort described. 

The typical (piicksilver retort for placer mines is a cast-iron pot with 
a tight-fitting cover in which a hole is tapped to accommodate the con- 
denser pipe. The capacities of such retorts range from a few to 200 
pounds of amalgam, or about a quarter pint to 2 gallons. They are listed 
in chemical-supply catalogs at prices ranging from $4 to $30, not includ- 
ing the condensers. The condenser commonly used with this type of 
retort is an iron pipe 3 or 4 feet long leading from the hole in the retort 
cover at a downward angle of 20 to 30" ; it is encased for most of its length 
in a considerably larger pipe through which cooling water is circulated. 
When heat is applied to the charged retort the mercury vapor enters the 
condenser pipe where it cools and condenses; it trickles down the pipe 
into a ves.sel placed under the open end of the pipe. In the treatment of 
a large amount of amalgam the temperature of the pipe might be raised 
to a point where some of the vapor would escape; therefore, a cooling 
device is necessary. 

The retort may be heated over a large bunsen burner, by a gasoline 
blow torch, in a forge, or in one of several types of furnaces built for the 
purpo.se. Very high temperatures are unnecessary, and a wood fire is 
considered better than a coal fire. The flame should cover as much of the 
retort as possible. 

A rigid, .strong .stand for the retort and condenser should be con- 
structed if the apparatus is to be used regularly. 

The retort should be coated on the inside with chalk, or painted with 
a thin pa.ste of chalk, clay, mill slimes, or a mixture of fire clay and graph- 
ite and thoroughly dried before putting in the charge. This prevents 
the gold from sticking to the iron, which sometimes causes trouble. 
A lining of paper .serves the same purpose but tends to form an objec- 
tionable deposit in the condenser pipe. 

The retort should not be filled over two-thirds full of amalgam (a 
third or half full when retorting liquid mercury), otherwise there is dan- 
ger of .some of the contents boiling over into the condenser tube. The 
amalgam is broken into pieces and piled loosely. Then the cover is put 
on and clamped tightly with the wedge or thumbscrew provided, first 
making sure that the attached condenser pipe is clean and free of obstruc- 
tions. The ground joint between the cover and body of the retort is 
•seldom tight enough to prevent leakage and should be luted with clay or 
some .sealing compound. One satisfactory cement is made readily by 
moistening a mixture of ground asbestos and litharge with glycerin. 

A low heat is applied at first, then after 10 or 15 minutes the tempera- 
ture is increased just enough to start the mercury vaporizing and con- 



Sec. I] HYDRAULIC MINING 137 

densingr. Too rapid heating harms tlie retort, and only enough heat 
should be used to maintain a steady trickle of quicksilver from the con- 
denser. When no more mercury appears the temperature should be 
increased for a few miiiutes to red heat to drive the last of the quicksilver 
out of the retort ; then the fire should be withdrawn from the retort and 
the latter allowed to cool. Some mercury vapor always remains in the 
retort, and the operator should take care not to breathe these fumes upon 
taking off the cover. 

The likelihood of dangerous amounts of mercury vapor passing 
through a long cold pipe without condensing is very small. However, 
if much amalgam is to be retorted, or if the operation is of daily or fre- 
quent occurrence, it usually is desirable to provide some form of water 
seal at the end of the condenser tube to prevent the escape of such fumes. 
Many miners have followed the dangerous practice of submerging the 
end of the condenser pipe in the bucket of water used to receive the con- 
densed mercury. This should not be done, as a slight cooling of the retort 
would cause water to be sucked into the pipe, and if the water reached the 
retort an explosion would follow. Such an experience has taught more 
than one "oldtimer" the danger of this practice. 

If the volume of the receptacle is very small compared with that of 
the condenser pipe and if the discharge pipe is barely submerged the 
danger is avoided, as any large rise of water in the pipe would lower the 
water surface enough to break the suction. At some properties the end 
of the condenser pipe is in a large sheet-iron cylinder, a few inches in 
diameter, open at the lower end, which may be placed 2 or 3 inches into 
the water in a receptacle of only slightly larger diameter, thus making 
a good water seal yet avoiding the danger of explosions. 

The simplest method is that recommended by Louis ;2" it consists 
merely of tying a piece of cloth such as canvas or burlap around the end 
of the condenser pipe and letting it dip in the water 2 or 3 inches below, 
forming a damp filter which will condense any escaping vapor yet not 
be tight enough to permit water to be sucked into the retort. 

Large gold mines use cj'lindrical retorts, usually set horizontally in 
specially built furnaces. Such installations probably would be needed in 
placer mining only by large dredging companies. The operation is 
similar to that of a pot retort, except that the amalgam usually is placed 
in several small iron trays, rather than on the floor of the retort proper, 
and charged through a door or removable cover at one end of the retort, 
while the condenser is attached at the opposite end. 

Separation of Platinum-Group Metals From Gold 

In several localities in the AVestern States sluice concentrates from 
placer mining are likely to contain platinum or its associated metals in 
sufficient quantities to be of economic interest. The .separation of these 
minerals from gold is difficult. Their specific gravity is too near that 
of gold to permit a separation by panning. Coarse platinum particles can 
be picked out of the gold by hand, but most placer platinum is exceed- 
ingly fine. Although platinum does not amalgamate, quicksilver can be 
made to coat and hold platinum particles by treatment with chemicals; 
thus it is possible to sepai-ate successively the gold and platinum from the 
concentrates. 



^ Louis, Henry, A handbook of gold milling, p. 38C, London, 1894. 



138 



•K.\< i:i{ minim; ion cold in cArji-oKNiA 



[liiill. l;]; 




See. T] iiYDRATirjc minino 139 

One dredging company in California wliich recovers platinum metals 
uses the following clean-up procedure :-" 

In cleaning up, the riffles arc removed from the sluices, starting at 
the head end, carefully washing them off and washing the sluice down 
with water from a hose. This washes away the light sands and concen- 
trates the amalgam and heavy sands, which are carefully scooped up into 
buckets and carried to a "long tom" for further treatment. In the long 
tom most of the mercury and amalgam and some of the platinum-group 
metals are caught in the upper box. Most" of the platinum, some rusty 
gold, scattered particles of mercury and amalgam, and the sand and ref- 
use are washed out over riffles where the heavier components are caught. 
The sand finally passes through a screen at the end of the tom, into a sand 
box, and the gravel goes to waste. The mercury and amalgam from the 
upper box are transferred to a bucket, in which the gold amalgam settles 
to the bottom ; the lead or other base-metal amalgams float on top. The 
latter is partially cleaned by panning, Avhich separates some metallic 
platinum, then retorted. The gold amalgam is squeezed free of mercury 
and likewise retorted. 

The gold amalgam, usually containing about 55 percent gold and 
silver, is retorted in a standard make of gasoline-fired retort. The mer- 
cury condenses in a w-ater-jacketed pipe and drains into a bucket of 
water. The gold remaining in the retort is transferred to a crucible 
and fused in the same furnace. It is then poured into molds, producing 
bars which are shipped to the Selby smelter. The bullion averages 890 
parts gold, 90 parts silver, and 20 parts impurities per 1,000. 

The riffle concentrates and sand from the end of the long tom are 
placed in small batches in a steel barrel mill 4 feet long and 2| feet in 
diameter. Mercury is added and the batch ground for 1 or 2 hours. 
Then the amalgam is removed by panning and added to the other base 
amalgam for retorting. Further panning and rocking reduce the remain- 
ing sand and concentrates to a product containing about half black sand 
and half platinum, by volume. This is treated by the addition of water, 
mercury, zinc shavings, and sulphuric acid ; this causes the platinum 
metals to be coated and held by the mercury, so that a final separation 
from the sand is possible. The final concentrate is then washed with 
water and drained to remove acid and excess mercury, after which treat- 
ment with nitric acid dissolves the mercury, leaving a final residue of 
platinum, iridium, and osmium. 

The base amalgam, which includes shot, bullets, and small particles 
of copper and brass scrap, as well as some precious metals, is retorted to 
recover the mercury, melted, and poured into molds to form bars for 
shipment to the smelter. These bars range in value from $1 to $8 per 
troy ounce. 

The United States Mint does not now buy platinum or pay for the 
platinum content of gold shipments. The following buyers of crude 
platinum reported purchases in 1930 -^"^ 

American Platinum Works, 22") New Jersey Railroad Avenue, Newark, N. J. 
Baker & Co., Inc., 54 Austin Street. Newark, N. J. 
J. Bishop & Co. Platinum Works, Malvern, Pa. 
Sigmund Cohn, 44 Gold Street, New York, N. Y. 



» Patman, C. G., Method and costs of dredging auriferous gravels at Lancha 
Plana, Amador County. Calif.: U. S. Bur. Mines Inf. Circ. 6659, pp. 12-13, 1932. 

^ Davis, H. W., Platinum and allied metals in 1930 : Mineral Resources U. S., 
1930, pt. 1, p. 105, 1931. 



140 PLACKK MINING TOU GOLD IN CALIFORNIA [Bull. 135 

Thonins J. Doo & Co., 1010 ^I.iIIcis Ruil<lin^', Chicago. 111. 

Kiistonliul.or & Ldirf.-hl. L'4 John Sln-ot, \c\v York, N. Y. 

rarific riatiiMiiii Works, Inc.. S14 Sondi S|irin>; Street, I,os AiikHcs, C-iIif. 

Schwittcr. CIomt & Slaitw r:ith<T. Inc., .".lli r.iss.iic Avenno, X.nvark, N. J. 

Wildberg llros. Smell in;; & Helinin- Co., 741! .Market Street, San Francisco, Calif. 

Lots ranging; from less tlian an ounce to hinidreds of ounces ordinarily 
are marketable but preferably not less than 2 ounces. .Settlement is based 
on assay, either by the buyer or, for larji^e lots, by both parties. The price 
paid in 1!)30 for domestic crude platinum ranj^cd from $30 to $40 per 
troy ounce ;-^ the average quotation for the refined metal was $45. 

Melting Gold ^ 

The spongy mass of gold left after retorting can be sold to the mint 
or other agencies just as it comes from the retort, but generally it is 
melted and poured into molds to form bars or ingots for marketing. 

The melting generally is done in graphite crucibles placed in a 
special furnace. In small operations the crucible is usually heated in a 
blacksmith forge in which coke is used for fuel. The graphite crucible 
must be dried thoroughly before it is used by being warmed gradually for 
several hours. 

Small quantities of gold frequently are melted without fluxes in 
make-shift devices such as dented frying pans ; in most instances, how- 
ever, .some flux is desirable. If the gold is fairly pure, that is, has a 
bright yellow color, it may be melted with only a small quantity of borax 
glass for flux. If, however, it contains impurities and is grey or black 
in color, the melt requires larger quantities of flux to take up these 
impurities. Sometimes niter, sodium carboiuite. or silica is used to 
remove specific impurities. The flux is melted first, then the gold is 
placed in the crucible and likewise melted. Enough flux is used to form 
a covering about one half inch deep over the molten metal. 

In large-scale operations the melted gold is poured from the crucible 
into cast-iron molds holding 50 to 1. 000 ounces. A mold should be larger 
at the top than at the bottom so that the bullion will drop out readily 
when it is inverted. A mold 3 inches by 12 inches at the top, 1 inch 
narrower and shorter at the bottom, and 3 inches deep holds about 1,000 
ounces. The common practice is to smoke the mold over an oil flame, 
then to heat it before pouring the gold. Another practice is to coat the 
mold with graphite or oil or to pour a (juarter inch of vegetable oil in 
the mold and heat it to boiling, then to i)our the gold into the oil. 

When the gold has just set in the mold and before the slag has hard- 
ened, the contents of the mold are tipped into water. This granulates 
most of the slag, aiul any particles still adhering to the gold usually can 
be bni.shed off. Tightly adhering slag can be loo.sened by washing the 
gold with nitric acid. 

The bar of bullion may be stamped with identifying marks or names, 
or these may be cast in reverse in the bottom of the mold. The bar is then 
ready for market. 

Sampling and Weighing Gold 
Sampling 

There are several methods of sampling gold bullion. The most accu- 
rate one is to dip a sample from the melted bullion before casting it. 

"Davis, H. W., op. cit., p. 105. 
^ ... "^'"^f «/'M Reserve Act of jyji. a Iicen.se from a U. S. Mint is required for 
melting gold. A copy of this act i.s available from Superintendent of Documents, (Jov- 
ernment Printing Office, Washington, D. C, for 10 cents. 



Sec. I] TivnHATTLic MiNixn 141 

A {graphite rod suitably shaped at one end to dip up the desired amount 
of gold, usually 1 to 5 f>rams, is heated redhot, stirred about in the melt, 
and lifted out with the sample. The sample is then poured into an oiled 
mold or into a .shallow bath of heated oil. This method has been used by 
a few mining companies and is said to eliminate slight inaciniracies to 
which other methods are subject. It is impracticable for small amounts 
of gold and is inconvenient in that the sample is not obtained in a form 
convenient for assay; except for bullion containing large (piantities of 
base metals, simpler methods generally are sufificiently accurate. 

Other methods depend on taking samples from the solid cast bar of 
bullion, (.'hips can be cut with a cold chisel from the surface of the bar, 
at one or more places, hammered thin, and trimmed to the desired weight 
for assay, or holes can be drilled aiul the drill cuttings used for samples. 
The latter method is used most. Holes an eighth inch or less in diameter 
are drilled a quarter to a half inch into the bar, usually one on top and 
one on the bottom of the bar, on the center line a short distance from the 
opposite ends. Two diagonally opposite corners, one on top and one on 
the bottom, are sometimes preferred, although the difference probably is 
negligible. It has been found that in bullion containing base metals there 
is a strong tendency for the base elements to segregate at the bottom of 
the bar and for the top surface to be above the average fineness. Special 
methods of sampling then must be used. However, for most placer-mine 
bullion a sample of the desired weight, obtained in almost any convenient 
fashion, will be sufficiently accurate. Drill samples taken as described 
above usually check the mint or smelter return within 5 parts per thou- 
sand. 

When gold is to be shipped to the mint, assaying the bullion is a 
needless expense as there is no recourse from the mint assay returns. 

Weighing 

Analytical balances suitable for weighing small amounts of gold with 
great accuracy" cost from $150 to $300, and balances that will weigh large 
amounts of gold, such as the gold bars shipped to the mint by mining com- 
panies, with sufficient accuracy so that their value can be calculated to 
the nearest cent, are very costly. Balances capable of weighing a few 
ounces of gold to the nearest cent can be purchased for $20 to $30, and 
convenient pocket scales, either of the hand-balance type or arranged to 
be set up on the cover of their cases as mounted balances and capable of 
weighing 3 or 4 ounces to the nearest cent, are sold by most chemical- 
supply houses at prices ranging from $2.50 to $15, including weights. 
With little or no expenditure a set of hand balances can be made, which 
will w^eigh 1 or 2 ounces of gold to within a grain or the nearest 5 cents. 
The balance beam may be of wood, 6 or 8 inches long, suspended by a pin, 
needle, or bent wire hook through a hole in the exact middle of the beam. 
The pans can be made of tin, cut 1^ to 2 inches in diameter and hammered 
dish-shaped, or of the lids of small tin cans, each suspended by three 
threads from the ends of the beam by means of bent wire hooks. No 
pointer is necessary, as the beam can be leveled closely enough by eye. 
It is not necessary that all parts be of exact weight, as the balance beam 
or the pans can be trimmed to make the assembly balance. For even 
approximate ^accuracy, however, it is necessary that the pans be sus- 
pended from points on the beam the same distance from the center bear- 
ing, and for stability the end bearings must be slightly lower than the 



142 I'I,A(i:k MisiNf; iok (ioi.d in rAMFOKNiv fllull.l'jr) 

center one. The nicer tlie const ruction and the more nearly frictionless 
the method of .suspension, the j^jreater tlie accuracy; hut even with very 
little attention to these points a sensitivity of less than a jrrain is obtain- 
able when wei«:hinjr as much as 2 ounces. Weijrhts can be purchased in 
convenient sets for ;")() cents or more or can be made or improvised from 
bits of wire or sheet metal cut to match any available standards. 

Marketing Placer Gold 

Five classes of buyers usually are available to the miner who wishes 
to sell }?old dust, retort spon-^'e, or bullion bar: (1) Individual gold 
buj'ers; (2) local stores; {:]) local banks; (4) smelting companies; and 
(5) United States mints and assay offices. If the miner has base bidlion 
or conceiitrates the smelter or custom mills are usually his only market. 

Local stores are the principal buyers of snudl amounts of gold, rang- 
ing in value from a few cents to $r)U or more. The merchant, who is often 
tlie chief retailer of supplies to the miners, finds it brings him trade to act 
as a connni.ssion buyer of gold, making it possible for the prospector and 
miner to convert their winnings promptly into cash. If his commission 
is fair, this is satisfactory, as it saves the miner much distasteful annoy- 
ance in preparing his gold for shipment, filling out various registration 
and report forms, and then waiting several days for his check. It like- 
wise makes possible the sale of less than 1 ounce of fine gold at a time, 
which is the least amount of retort sponge, gold dust, or nuggets the mint 
will accept. The discount of the merchant ranges from $1 to $2 per fine 
ounce. The miner must remember that no placer gold is pure and that 
the merchant has only his judgment to tell him how much the mint will 
pay for his gold. Not all gold from a district assays the same degree of 
fineness, and the merchaint is not to be blamed for staying on the safe side. 

In most mining districts there are assayers, company officials, jewel- 
ers, metal brokers, or other individuals who for profit or for the conven- 
ience of employees, lessees, or customers make a practice of buying gold 
in small lots from prospectors and miners and paying cash for the value 
of the estimated weight of fine gold, less certain charges. Likewise banks 
in many districts receive gold, either purchasing it outright on the basis 
of their own or commercial assayers' anal,yses, or merely acting as ship- 
ping agents, receiving the gold, shipping it to the mint, and paying the 
miner upon receipt of mint returns. In the latter case a connni.ssion of 
about 1 percent usually is charged, for which the bank assumes all risk 
and trouble otherwise taken by the miner himself. 

A few smelters or refineries buy gold or silver metals; the melting 
and refining charges probably will closely approximate those of the mint. 
Most smelter or refineries handling precious metal ores buy gold-bearing 
concentrate. Smelting charges on such material are variable, and an 
inquiry, accompanied by a close description or a sample of the material 
offered for sale, should be made in advance. 

(Jold can be shipped by express or by mail. If by express, the parcel 
can be insured with the express company for its full estimated value. 
United States mail shipments usually are sent as registered first-class 
mail and should be insured. The mail registry .system provides insur- 
ance in graduated amounts from $5 to $1,000 at a cost of 15 cents to $1, 
including the registration fee but excluding po.stage. If regular mail 
shipments of considerable value are being made, it is possible to secure 
commercial insurance for them. However, for amounts greater than a 



•Sec. I] iivnuAur-ic MINING 143 

few oiniees the first-class postajxe rate of 3 cents per ounce becomes so 
costly that express shipments are advisable. All shipments must be pre- 
paid. 

The best container for shippin*,' f^fold, either by mail or express, is a 
lead-sealed canvas sack, securely tagj^ed with the addresses of the sender 
and addressee. Gold bars may be wrai)ped securely in canvas and packed 
in wooden boxes. 

When a shipment of gold is sent to the TTnited States Mint a letter 
should be sent sepaVately containing the. prescribed affidavits. Form 
TG-in, for a person shipping gold that he has mined himself, and form 
TG-21, for gold buyers, can be obtained by writing to a United States 
mint or assay office. Form TG-lf) need not be sworn to if the amount of 
gold is 5 ounces or le.ss. Since January lO.'U the mints have paid $35 per 
troy ounce of fine gold, less one-fourth of 1 i)ercent, as compared with 
the former price of $20.67-}- per ounce. 

"The mint charges $1 for meltiiig any deposit of 1,000 ounces or less 
and 10 cents additional for each 100 ounces over this amount. An extra 
charge of $1 or more is made for melting gold dust or gold containing 
non-metallics if the loss of weight in melting is more than 25 percent. 

If the gold is 992 fine, or finer, no charge is made for parting and 
refining. If less fine, or if more than 50 parts base metals are present 
per 1,000, charges of 1 cent to 5 cents or more per ounce are imposed for 
parting and refining. Bullion less than 200 fine is not accepted. 

Current market prices are paid for the full silver content ; however, 
if necessary forms are submitted for silver qualified under Executive 
Proclamation of December 21, 1933 the depositor will receive the number 
of silver dollars that can be coined from one half of the fine silver content. 
No other constituent in the bullion is paid for. 

Laws Regulating Ore Buyers 
California laws reciuire ore buyers to take out licenses. The Cali- 
fornia Ore Buyer's License Act, passed in 1925, includes as buyers all 
persons sampling, treating, or buying gold dust, gold or silver bullion, 
gold or silver specimens or ores, or concentrates of these metals and gives 
the Staje ^Mineralogist the duty of licensing such persons.^*^ The license 
fee is set at $15 per year if the gold and silver treated or purchased in a 
year exceed $1,000 in value oi- at $2 if less. The licensee is required to 
keep on record the names of the sellers, the amount and description of 
each lot purchased, the stated source of each lot, and other data and to 
report all purchases monthly to the State ]\Iineralogist. Provision is 
made for the issuance of licenses, recovery of stolen metals, and penalties 
for violation of tUe act. The latter are severe. No regulation, of course, 
is placed upon the gold buyer as to terms of j)urchase, nor is this a matter 
of record under the act; however, one effect of the act, which primarily 
is intended to prevent the ready sale of stolen gold oi- silver, doubtless 
is to improve the chances of the small producer getting fair treatment 
from ore buyers b\' driving dishonest dealers out of business. 

»>Rickett.s, A. H., American mining law: Calif.. inia |iiv. Mitu-s Hull. IL':!, pp. (JOI)- 
664. 1943. 



144 PLACER MINING FOU GOLD IN CALIFORNIA [Bull. 135 

DEBRIS DAMS 

When Indraulic mining was at its heip^ht, annual production of gold 
by that method reached $1 ;"),()()(),()()(), and averaged $1(),()00,()00 per year 
for the 30 years ending in 1884.^ Tlie best estimates- of the amount of 
gravel that was mined to recover this gold indicate that 1,205,000,000 
cubic yards was washed into tributaries of the Sacramento alone. This 
is equivalent to a body of gravel 10 miles long by 1 mile wide by 125 
feet deep. 

' ' The immense scale of these operations caused serious silting of the 
river channels and partial blockage of streams tributary to them, so that 
in flood times much damage was done to farm lands adjacent to the rivers.. 
In conse(|uence there were many actions at law in the State courts, which 
resul-ted in injunctions against the mines. Immediately prior to the 
general closing of hydraulic mining the annual yield is estimated to 
have been reduced to $5,300,000.3 

Finally the decree of Judge Sawyer of the United States Circuit 
Court restrained the North Bloomfield Mining Company from discharg- 
ing debris into the streams. Tliis was in 1884. The court reserved the 
power to modify or suspend the injunction upon the defendant's showing 
that conditions had been so changed that the discharge of debris might 
be conducted so as not to continue the nuLsance complained of. That 
is to say, hydi-aulic mining was not declared to be illegal, but the dis- 
charge of debris into the streams was forbidden. The provision of a 
dam to restrain the debris might make the necessary change in conditions 
to allow mining to be resumed. 

Mine after mine was closed by injunction based upon this decision 
and the federal legislation pas.sed in 1893 (the California Debris Com- 
mi.ssion Act, or Caminetti Act) embodied the principles declared by these 
injunctions, but enacted moi-e severe penalties for their non-ob.servance. 
The Caminetti Act is printed in full in the appendix of this bulletin. It 
applies oidy to the territory drained by the Sacramento and San Joaquin 
iJivcrs. 

Under the Caminetti Act, charges for debris storage behind dams 
contemplated by the law were set at 3 percent of the gross proceeds of 
a mine. As this was inadequate to amortize the cost of such dams, the 
Caminetti Act was in effect more than 40 years before any debris dams 
were built. An amendment approved June 19, 1934, set the charges on 
the basis of cubic yards of gravel mined behind the dam. The matter 
of building such dams by the Federal (Jovernment was reviewed by the 
California Debris Commission, and a report^ containing recommenda- 
tions against the building of debris dams was submitted to the Board of 
Engineers for Kivcrs and Harbors under date of February 13, 1935. A 
hearing in j)n)tcst of this report was held before the Board of Kivers and 
Harbors in Washington on Ai)ril 15, 1935, and Walter W. Bradley, Cali- 
fornia State Mineralogi.st, presented before that board a brief to show 
the value of placer gravel that would be made available for mining behind 

• .larman, Arthur, An inve.stiRation of "the feiisil)ility of any plan or plan.'^ whprehy 
hydraulic niiiiiiiis' opiration.s can be resumed in thi.s .state" ; California State Min. Bur., 
MinlnK In California, State Mineralopi.st's Kept. 2.i, pp. .'".4-1 1(1, iy27. 

3 LlndKreii, Waldeniar. The Tertiary gravels of the Sierra Nevada of California: 
U.S. C.eol. Survey Prof. Paper 73, p. :i], IHI 1. 

'Haley, C. S., Gold placers of California: California State Min. Bur., Bull. 92, 
p. 16, 1»2:{. 

< Jackson, T. H.. Irvine, E. S. J., and Drinkwater, J. C, Report of the California 
Debris C'immis.sion : 74th Cong., l.st .m-.s.s., H. Doc. .50, pp. 9-34, 5 niap.s, llt.J.'i. 



Sec. I] DEBRIS DAMS 145 

such dams. Tliis brief was publislied in the July 1935 issue of the Cali- 
fornia Journal of Mines and Geology. •'"' A map shows locations of pro- 
posed dams. 

The Board of Engineers for Rivers and Harbors'* under date of 
May 23, 1935, reported in favor of the construction of four dams at a 
cost of $6,945,000. The dams recommended were the Upper Narrows 
dam on the Yuba River about 1^ miles above its confluence with Deer 
Creek near Smartsville ; Dog Bar dam about 7 miles up the Bear River 
from the existing Combie dam or 3 miles southwest of Colfax; the North 
Fork dam on the North Fork Americaii River about 2 miles above its 
confluence with IMiddle Fork American River near Auburn ; and Lower 
Ruck-A-Chucky dam on Middle Fork American River a mile below the 
mouth of Canyon Creek. 

An appropriation was provided by Congress, and two of these dams 
were built in the late thirties, and are now ready for use, the Upper 
Narrows dam and the North Fork dam. In an announcement dated 
January 5, 1942 the California Debris Commission established a tax 
rate of 3.11 cents per cubic yard for storage of hydraulic mining debris 
in the North Fork Reservoir on the North Fork of the American River, 
and a tentative tax rate of 2.30 cents per cubic yard for storage of debris 
in the Upper Narrows Reservoir on the Yuba River. Power is generated 
at the Upper Narrows, and this helps to pay for the dam, as provided in 
an amendment to the Caminetti Act approved June 25, 1938. This 
amendment is printed in the appendix. 

Work was started on the Lower Ruck-A-Chucky dam, but the rock- 
formations at the proposed site were found unsuitable to support the 
dam, and the site was abandoned. If a dam is built to restrain debris 
on the Middle Fork of the American River, a new site farther up the 
stream will probably be selected. On the Bear River, where the Dog 
Bar dam was to be constructed, a conflict exists with regard to the genera- 
tion of power, and trouble has been caused by mud and silt in the water 
at the existing Combie dam. This conflict of interests makes plans uncer- 
tain for a debris dam on the Bear River. On the Yuba River, a mile 
beloAV the mouth of Willow Creek, near Camptonville, the Bullard Bar 
dam owned by the Pacific Gas and Electric Company has been available 
for storage of hydraulic mining debris for many years. The charge per 
cubic yard in 1941 was 2 cents. 

Although the two debris dams mentioned above have been built and 
are ready for use, some serious problems still remain to be solved before 
hydraulic mining can be resumed on a large scale. One of these was 
brought out by case no. 60,474 in Department 4 of the Superior Court of 
Sacramento County, Carmichael Irrigation District and others vs. Lost 
Camp Mining Company and others. Carmichael Irrigation District 
alleged that damage was being caused by mud and silt from hydraulic 
mining above the North Fork dam on North Fork American River near 
Auburn. A temporary restraining order was issued in 1939 against 
hydraulic mining during the irrigation-season. This order allows 
hydraulic mines on North Fork American River to operate only between 
November 15 and April 30. McGeachin Placer Gold Mining Corporation 



5 Bradley, Walter W., Dams for hydraulic debris : California Jour. Mines and 
Geology, vol 31, pp. 345-367, 1935. 

« Pillsbury, G. B., Control of mining debris on the Sacramento River and tribu- 
taries : 74th Cong., 1st sess., H. Doc. 50, pp. 3-8, 5 maps, 1935. 

10—56968 



140 i'(,.\( i;iv minim; ioi; (;iii.i) i\ ( amiouma | Uiill. i:!.') 

jiiid Tlic .M;i\ flower (iravcl .Miiiiii;^' ('oiiipjiiix- filed answers in this case 
ill .Maivh 1!M:; all('^iii<; that the I'liited States ( ir>veniiii<'iit is a party 
in interest and that the ease sh(»nld he translen-ed to a l^'edoi-al court. 

A second serious ))rohleni is th^^t oi" water-supply. IMauy of the ohl 
water-rij:lits. and even some of thc^'-imclK^s formerly used l)y hydraulic 
mines have heen ac(piired by power companies and irrijiati(ni districts. 
Where the old water ri<ihts are no lon<ier available, the only practicable 
metlnwl of replacing' them is by the stora<;e of surjdns water by means of 
larjic i-eser\<)ii's lii<:h in the monntains. This is, of course, expensive. 
Even \\her(> wat er-ri^zlits have been retained by hydraulic minin;,' com- 
]ianies. many of the ditches and tliinies refpiire rebuilding'. 

])ecaiise of these difliciillies. mnch consideration is bein^' '/iveu by 
owners of lar^c jrold-l)earin^- <ira\el deposits to meciianical methods of 
handling' <:ravel with tailing- stora^jc at the. mine as a substitute for 
hydraulic mining-. Such methods are rapidly bein;^- reduced in cost, and 
may soon become available. ])redj:inji: may be used for some of the 
<lei)osits. but many of the larjie dei)osits are too deep for any dredge yet 
constructed. 



SECTION 



GEOLOGY OF PLACER DEPOSITS 



NEW TECHNIQUE APPLICABLE TO THE STUDY OF PLACERS* 

By OLAK 1'. JKNKINS **' 

OUTLINE OF REPORT 

THKe 

ABSTRACT 1^<> 

INTRODUCTION 1''^ 

Object of the report 1-jl 

Significance of improved exploration methods ]-j2 

Aerial photography l'j3 

Geophysical surveying l-jS 

Physiography lij3 

Study of desert processes l^'*^ 

Stream sedimentation l'>3 

Usefulness of contouring an ancient surface 1">4 

Provinces of the ancient channels in California I'tH 

Economic significance of the Tertiary gravels 1[)7 

History of development 1">0 

CLASSIFICx\.TION OF PLACERS 161 

Outline of classification 161 

General statement 162 

CHARACTERISTICS OF THE PRINCIPAL TYPES OF PLACERS 163 

Residual placers 163 

Eluvial placers 163 

Stream placers 163 

Glacial-stream placers 165 

Bajada placers 166 

Eolian placers 167 

Beach placers 168 

PRESERVATION OF PLACERS 171 

MODIFICATION OF PLACER DEPOSITS 171 

GOLD IN PLACERS 173 

Original source of gold 173 

Release of gold from bedrock 174 

Associated minerals 175 

Transportation, deposition, and retention 178 

Factors of concentration 181 

AGE OF PLACERS 183 

Significance 183 

Structural criteria 183 

Paleontologic criteria 184 

Physiographic criteria 185 

Lithologic criteria 185 

Coordination of criteria . 186 

LIFE HISTORY AND HABIT OF STREAMS 186 

Need for scientific background 186 

Stream erosion 187 

Preparation of material removed by erosion 188 

Transportation 188 

Deposition 191 

Physiographic terms relating to streams 194 

Desert processes 197 

Need for establishment of working criteria 200 

GEOLOGIC CONDITIONS IN THE GOLD PROVINCES OF CALIFORNIA 200 

CONCLUSION 206 

BIBLIOGRAPHY OF CALIFORNIA PLACERS 208 

* Reprinted from April 19 35 California Journal of Mines and Geology, pp. 143-210. 
•* Chief Geologist, California State Division of Mines. 

(149) 



150 



rLA(i;K MIMNC K()|{ COIJ) IN CAI.I lOKN'IA 



[null. 1:55 




Fig. 46. Aeri 
the dredge at work 
Journal. 



iKrapli of a dredseil .'^trip alonp the Yuba Ri\( r ; 
u by Russell; reprinted from Engineering and Mt 



Abstract 
Tho exploration of placers is a problem involving' nearly all i)hase.s of the seionce 
of >,'eolo{,'.v, especially physiography and streani sedimentation, neither of which has 
i>e<'n piven sufficient consideration in connection witli the economic problems concerned. 
The use of aerial photography is a great aid in the study of placers, both ancient and 
modern. The use of geophysics, when applied as a part of a geologic program of explo- 
ration, can materially assist in guiding drilling operations and underground prospect- 
ing, with the result that the cost of expensive development work can be greatly reduced 
and hastened to an earlier completion. 

Placers arc classified according to the way they are formed : residual, eluvial, 
stream, glacial-stream, bajada, eolian. and beach. Since the ordinary stream placer 
is by far the most important, various phases of stream study are discus.sed in this paper. 
A need for further scientific study and the development of systematic working criteria 
is apparent. 

The deideted placers of California consist largely of Recent and Pleistocene stream 
gravels and uncovered or buried, but easily accessible Tertiary channels, while the large 
reserves lie in more remote positions. These are exemplified by hidden buried bench 
gravels not connected with the surface nor with channels already worked, and by the 
lower untouched channels that lie on true bedrock beneath the 'false bedrock' of the 
dredged areas along the western foot of the Sierra Nevada. Some Pleistocene gravels 
still lie in pockets beneath the waters of the larger rivers where faults have caused 
down-dropping of the streani bed. Benches still lie in isolated regions such as the 
Klamath Mountains. The desert affords several types of deposits: stream placers 
buried by alluvial fans, reworked older placers, gravels interbedded with lavas, and the 
more recent bajada placers. !SIarine placers of Cretaceous, Eocene, Pleistocene, and 
Kecent periods exist in the state, which may in places be worth investigating. 

The largest of all these possible reserves in California probably lies in the remain- 
ing buried Tertiary streani channels of the Sierra Nevada. 



See. IIJ 



(lEOLOCY OF PLACKK DKPOSITS- -JENKINS 



151 




Fig. 47. A mined-out segment cf the Tertiary Central Hill channel near 
Murphy, Calaveras County. Wliite rhvdlitic a.-<h, which covered this cliannel, is 
exposed on the left. 

Introduction 

Object of the Report 

The gold-bearing gravel tlepo.sits or placers of California that still 
remain untouched lie, for the most part, in more obscure positions than 
the depleted gravels which formerly produced vast wealth for the state. 
The depleted gravels, which Avere once readily accessible but are now 
nearly mined out, fall into three principal classes: 

Depleted placers 

1. Keci'iit and Quaternary stream gravels. 

2. Uncovered channels of Tertiary age. 

3. Buried Tertiary channels, easily located. 



About one billion dollars worth of gold came from these three 
sources, the first having produced twice as much as the other two put 
together. 

The placers which still remain to be sought out and worked, offer a 
challenge to the ingenuity of the exploration geologist. The problems 
involve the following types of deposits : 



152 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

Placer rcacnrii 

1. Deep gravel deposits lyinR immediately beneath several large rivers, 
such as the Feather and Klamath. 

2. Isolated high benches such as those found in the Klamath Mountains. 

3. Ancient gravels that lie beneath 'false bedrock' (interbedded volcanic 
layers) of the dredging areas along the western foot of the Sierra Nevada. 

4. Gold-bearing gravels occurring in the 'shore' deposits of the lone 
(Eocene) formation, and the Chico (Cretaceous) formation. 

5. Buried Tertiary channels and associated benches located in the known 
gold-bearing districts of the state. 

6. Buried Tertiary channels and benches in the lava-covered district which 
lies between the Sierra Nevada and the Klamath Mountains. 

7. Bajada placers, or desert alluvial-fan deposits, where gold is derived 
directly from the original mineralized bedrock source. 

8. Desert placers, where the gold is reconcentrated from more ancient gold- 
bearing streams. 

9. Buried desert stream placers. 

The scope of these problems indicates the great need of an under- 
standing of the geological principles involved. In no kind of mining is 
geology more applicable than in the exploitation of these more obscure 
placer deposits. For this reason, the following discussion is written. 

Significance of Improved Exploration Methods 

A widespread geologic study of the ancient Tertiary gold-bearing 
stream channels of the Sierra Nevada, the gravel deposits of which are 
found to a large extent buried beneath a mantle of volcanic materials, was 
concluded by the United States Geological Survey a quarter of a century 
ago. Lindgren's "Tertiary Gravels'" summed up, in a splendid man- 
ner, in 1911, these various geologic studies. His data were drawn from 
his own careful observations, from those of his associates, II. W. Turner, 
F. L. Ransome, and J. S. Diller (issued largely in folio form), and from 
such early sources as J. D. Whitney, W. H. Storms, and Koss E. Browne. 

Lindgren's Colfax folio,^ published in 1900, was the last great 
detailed field study of this kind in the Sierra Nevada. By no means, 
however, is this folio confined to the subject of stream channels, for it 
deals with every phase of the geology of the quadrangle. Everything of 
importance which it was possible to accommodate on a map of the small 
scale used — two miles to the inch — was recorded. At the time this field 
work was done, the best equipment and finest technique of the day were 
employed, and very little escaped Lindgren's keen observation, each fea- 
ture being scrutinized and shrewdly interpreted by his masterfnl mind. 

Since then, however, considerable advance has been made in explo- 
ration technique; other and different points of vantage are now avail- 
able ; and a greater degree of refinement of study is therefore in order. 
Furthermore, mining itself has many advantages today over the earlier 
methods. With the recent enormous advances in development of motive 
power, pumps, and other machinery, the drift-mining industry could 
easily undergo a greatly accelerated development, if guided by intelligent 
exploration carried on in advance of the attempt to extract ' pay ' gravel. 

' Lindgren, W., The Tertiary gravels of the Sierra Nevada of California : U.S. Ceol. 
Survey Prof. Paper 73, 226 pp., 1911. 

'Lindgren, W., U.S. Geol. Survey Geol. Atlas, Colfax folio (no. 6G), 10 pp., 
maps, 1900. 



Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 153 

Aerial Photography. From the air, regional photographs are syste- 
matically taken by qualified aerial photographers.^ The pictures are 
then examined under tlie stereoscope, or used in constructing topographic 
maps ^ Avhicli show the most amazing completeness of detail. Many sur- 
face features never before realized are thus simply unfolded before the 
eye. Geologic truths in great numbers are revealed, and many important 
problems solve themselves. Used as a base for location of field observa- 
tions and surface mapping, these aerial photographs are unexcelled 
They are undoubtedly the greatest practical aid which has yet reached the 
hands of the geologist ; besides they give secrecy, speed, and low-cost 
surveying to the program of modern exploration. 

Geophysical Surveyinr/. Added to this regional view from the air 
is the greater insight into the very interior of the earth itself afforded 
by several types of geophysical instruments, now well-tried and stand- 
ardized. Peculiar characters of rock structure and composition are not 
only revealed but measured with precision by skillful engineers. Since 
the proper interpretation of all results thus obtained requires sound 
geologic reasoning, it is important that a better and more detailed back- 
ground of geology should be drawn, and this is made more effective by 
aerial photography. 

Physiography. The subject of physiographic geology or geomor- 
phology has in recent j^ears made notable progress in developing sound, 
scientific principles concerning the history and origin of the present sur- 
face configuration of the earth. Since these principles are directly appli- 
cable to the more ancient earth surfaces of the Sierra Nevada, over which 
flowed the Tertiary streams now extinct. Tertiary physiography is the 
key to the ancient channel problem. 

Study of Desert Processes. Recent study of the geologic processes at 
work in the desert has led to a better understanding of the desert placers, 
which offer a practically virgin field for exploration, holding a potential 
wealth not yet knowTi. 

Stream Sedimentation. Furthermore, the study of sedimentation 
has now reached a refined stage of development. There are today avail- 
able various methods of technique which may be, but have not yet been, 
extensively applied to stream deposition. This sort of research includes 
the critical study of texture and structure of strata, as well as the micro- 
scopic examination of their mineral grains. It should yield a wealth of 
practical information concerning the processes involved in the accumu- 
lation of gravels, in the nature and direction of stream flow, in knowledge 
of what to expect as regards the concentration of gold and other heavy 
minerals, and in the correlation of channels of the same period or of the 
same system. 

The more obvious criteria of stream sedimentation have long been 
used by the experienced miner, who, by examining the gold particles 

' Lee, Willis T., The face of the earth as seen from the air ; a study on the applica- 
tion of airplane photography to geogrraphy : Am. Geog. Soc, Special Pub. 4, 1922. 

English, Walter A., Use of airplane photographs in geologic qiapping : Am. Assoc. 
Petroleum Geologists Bull. 14. pp. 1049-1058, 1930. 

Eliel, Leon T., Aerial photography and its importance to California geologists: 
California Div. Mines, Mining in California, State Mineralogist's Rept. 26, pp. 64-71, 1930. 

Eliel, Leon T., Aerial photography proves its importance to California geologists : 
Oil Bull., vol. 15, pp. 1177-1181, 1253, 1929. 

* Haquinius, E., and Shuster, E. A., Fr., Construction and operation of the Huger- 
shoff aerocartograph : U.S. Geol. Survey, Section of Photo-Mapping, 1929. 



154 



I'LACKH MINING KOU GOLD IX CALIFORNIA 



[liull. l:!.") 




Fin. 4S. View north(:'ast towanl Table .Mowitain, Tnulunme County, 
how this resistant lava flow, which filled a canyon cut in earlier vulcanic materials, 
now stands out in relief, while the surrounding cot'.ntry is eroded from its sides. 
Photo by Hurt Beverly. 

under tlio simple liaiul lens, infers whether tiiey were robbed from earlier 
cliaiinels or whether they eame direetly from a vein. Also he uses tlie 
'shingliufi' of <iravels to tell him the direetiou of stream flow. Tliese and 
a few other workiujr eriteria now used by the miner, however, have not 
all underjione a thorough seientific test, and at present thei-e is a wide 
differenee of opinion as to their interpretation. 

The advanees in technique and sound geolop;ic interpretation should, 
therefore, be made to serve as wide practical aids in channel exploration, 
and much more definite and conclusive result.s should be {rained now than 
were possible 25 years ajro. Since it is well known that many channels 
still lie buried, undoubtedly containiuf]: a potential p:old wealth not yet 
half exhausted, why should not new discoveries now be made if the new 
teehnicpie in placer exploration is employed? 

Certainly the more advanced methods of techni(|ue in exploration 
were called upon by the petroleum industry, resultino- in the floodinjj; 
of the country with oil. Now the application of some of the same methods 
is takinjr a leadino; part in various types of mining:, brinijiiifr further 
success to other mineral industries. If the prravel mininp: industry takes 
full coofuizance of the importance of the new exploratory methods of the 
science, successes for it should indeed be assured. 

Usefulness of Contouring an Ancient Surface 

The most elucidatiufr method of tracinp: in detail and showing graphi- 
cally tlie position and course of an ancient stream valley is by preparing 
a contour map '• of the old draina<re surface. The contours may be super- 
imposed over a base map which should also show the present surface 
topography and areal distribution of the geologic formations, as well as 
any mine workings, drill lioles, etc. 

AVitli the old surface contours superimposed on the present surface 
contours , an accurate estimate may be made of the thickness, extent, and 

" Lindgren, W., The gold-quartz veins of Nevada City and Grass Valley districts, 
California: U.S. Geol. Survey, 17th Ann. Rept., pt. 2, pi. II, 1896. (Contour map of 
Neocene bedrock surface.) 



Sec. 11] CKOUKiY OF PLACKK DFPOSITS— JKNKINS loS 



■/n 



B 

Fir,. 49. A, Kffort of stream-bed irregularities on water current. After Chamber- 
lin ciiid Salisbury. B, •SliiiiKliim'. The arrow points in the dirertion of stream flo\y. This 
arrangement of flat stones iiia.v be found in the bed of a mountain stream and is used 
by the drift miner to tell which way the ancient stream was flowing at that particular 
point. After Geike; orifiinalUi from Jamirson, T. G., Quarterly Journal, Geological 
Society of London, ml. ir,, /SoO. 

yardag'e of the intervening cliannel-filled area. The points which are 
to be nsed in preparinfj; an old-surface contour map should be secured 
through careful study of geologic and physiographic conditions, and 
obtained during the surface and underground survey. Drill-hole data 
and the essential results of geophysical observations should also be rep- 
resented on this map. Careful enough study should be made so that the 
points used represent only one period of erosion. 

If the geologic work is done prior to a contemplated geophysical 
survey and drilling program, much time and money may be saved in 
the location and number of points of observation, as well as in the 
number of drill holes needed. An approximate old-surface contour 
map may generally be constructed as a preliminary step by a skillful 
geologist, though he is limited only to surface data. This map should 
locate the general trend of the ancient valley to which later detailed 
work should be confined, thus eliminating much unnecessary and more 
costly work in adjoining areas unlikely to be productive. The most 
accurate elevations are those taken on bedrock where it is in direct con- 
tact with the older gravels, or with the pipe-clay and other volcanic 
materials of the oldest period of the area. Thus geological investigation 
should limit the extent of the geophysical work, which in turn defines the 
area to be drilled and later to be explored by underground methods. 

The basis for such mapping may effectively be prepared as part of 
a plane-table survey of the surface topography and geology. Aerial 
photography, however, has now become an almost indispensable aid to 
such work. Enlarged aerial photographs may be used as plane-table 
sheets, thus adding to the final map an enormous amount of useful infor- 
mation and physiographic detail. 

Provinces of the Ancient Channels in California 

The .so-called 'buried channels' occur for the most part in the north- 
ern Sierra Nevada, where, during the Tertiary period, millions of years 
ago, volcanic outbursts with their mud-flows, covered the then existing 
network of stream courses. Thus entrapped and preserved, this old sur- 
face of the earth, probably Eocene in age, with all its forest-covered hills, 
beautiful valleys, and Avinding streams laden wdth gold, 'became com- 
pletely hidden. Not until the area was lifted by mountain-making forces 
did the later rivers cut their canyons through the heavy mantle and 
expose whatever was bfeneath it. But even then, further volcanic mud- 
flows, cobble-washes, and newer streams of lavas, filled and refilled the 



Mfi 



rr.A( i:k Mixixr; for cold ix ("At.ifornia 



Bull. 135 




Fio. 50. Example of a Rcolngic map showing the earlier prevolcanic topog- 
raphy in contrast with tlx- prisent topography. Olii-surface contours (dashed 
lines) are drawn over prc^ent-siirfarH^ contours (fine, full lines). A major early 
Tertiary valley is thus reconstructed, ami the general position of its hurled stream 
channel is indicated, lying beneath volcanic materials of two later geologic periods, 
i.e., (1) Miocene cobhle and pipe-clay (mud flows and lake beds), and (2) Pliocene 
lava flow which followed a canyon cut in the andesitic materials. The older chan- 
nel cut In bedrock is gold-bearing. Its course was controlled by bedrock, for it fol- 
lowed the contact between hard diorite and softer schist. The gradient of the lava 
flow is not as steep where it is directed south as where it turns toward the west. This 
is explained by the westward tilting of the Sierra Nevada. 



Sec. 11] (iixiLocv oi' I'J;A(i;k |)i;i'()si'I's -.ii;.\1vI.\s LIT 

valleys formed. Finally, modeni canyoii-outliii<j: trenclicd the whole 
area deeply. leavin<r remnants of ilat-topped ridges between. 

Thonfzli no vok-anie mantle ever eovered the ancient streams of the 
Klamath Monntains, the ]-e^ion was uplifted in late Tertiary and Quater- 
nar}^ times, and the rivers uere therefore entrenched. As a residt, 
benches of p:ravel were left at various elevations alon<? the sides of the 
canyons. Faulting- also played an important role in tiie history of the 
uplift, trappinj; <>old-hearinp- pravels which date back to the Eocene." 
The whole .subje(;t of the sui-face features of the region, past and present, 
represents a series of vei-y interesting problems Jiot 3'et entirely solved, 
though they arc now- being carefully studied. 

In the Mojave Desert,' Tertiary gold-bearing streams may have once 
flowed south from the region which is now the Sierra Nevada ; but during 
the Pleistocene period their deposits became so broken and disrui)ted by 
faulting, and so extensively covered by later desert wash, that now there 
renuiins little to be easily recognized or traced. 

The problem of the 'dry i)lacer' is one of considerable importance, 
and when more is learned about it, an innnense potential gold wealth may 
be discovered which has not yet been glimpsed. At present, the lack of 
water * is largely responsible for limited operations. It is quite possible, 
however, to find and develop a sufficient underground water supply in 
many places for dredging operations. The finding of such water sup- 
plies may also be greatly assisted through the use of geological knowledge 
and geophysical surveying. 

In the Peninsular Ranges of San Diego County, some placers have 
been mined. In the Poway (Eocene)^ marine conglomerate is found the 
Ballena placer,'" described as early as 1893. 

Economic Significance of tlie Tertiary Gravels 

Lindgren'' in 1911, made the statement that "about $300,000,000 
is a conservative guess for the amount obtained from the Tertiary 
gravels," including hydraulic, drift, and other forms of placer mining. 
Ju.st how much has been taken from the buried channels by underground 
metliods, alone, is difficult to determine. J. M. Hill '" states : 

"Drift raining on the ancient buried channels was slarted at Forest Hill, Placer 
County in 1852 and was an important source of placer gold, by ISGG. During the period 
beginning about 187G and continuing to about 181)0, drift mining was most productive." 



" Hinds, Norman E. A., ]Mesozoic and Cenozdic eruptive rocks of the souUiern 
Klamath ^Mountains, California: Univ. California, Dept. Geol. Sei., JJiill., vol. :iu, i). 
3G8. 1935. 

" Ilulin, C. D., Geologic features of the dry placers of the northern ^Mojave Desert : 
California Jour. Mines and GeoloKy, vol. oO, pp. 417-J2(i, 1!)34. 

* Simpson, E. C, Geology and mineral deposits of the Elizabeth Lake quadrangle, 
California : California Jour. Mines and Geology, vol. 30, p. 4 09, 1"J34. 

Donnelly, Maurice, Geology and mineral deposits of the Julian district, San Diego 
County, California : California Jour. xMinos and Geology, vol. 30, p. 3ti:t, i'.r.'.r,. 

1" Merrill, Frederick J. II., The counties of San Diego, Imperial: California Min. 
Bur., State Mineralogi.sts llept. 14, p. 052, 1'J14. 

Fairbanks, H. \V., (Jeology of San Diego County, also portions of Orange and San 
Bernardino Counties: California 2Min. Bur., State Mineralogist's liept. 11, p. 'Jl, 18a3. 

" Lindgren, \V., The Tertiarv gravels of the Sierra Nevada of California: U.S. 
Geol. Survey Prof. I'aper 73, p. 81, 1911. 

12 Hill, J. M., Historical summary of gold, silver, copper, lead, and zinc produced in 
California, 1848 to 1920 : U.S. Bur. Alines, Econ. I^aper 3, p. 0, 1929. 



158 



I'LACKK MININn FOR fiOLD I\ ( AI.I l( IKNTA 



[Bull. 135 




Ki 



.Mil' -r 



til.' II 
til.- I 



<\ \\u 



•II M.rni .\.v;i.l:i. lli.' KI:iiii;Uh M ..mil ;i ins. 111.. i:r.:it i:.isi 
^.•il. <:..!. I liiis Im-.h mill,., I ill 111,- I', iiiiisiihii- l:,iiin,'S. ini.l ,i miimII aiiK.mit 
iKis I... 11 r,.mi,l ill 111,' siMitlurii (",.asl ll:iii;;,s. H was (itsf ,lis,'..v.i<'.l in 1 s:i I in (lu- 
Traiisv.Ts.- Ita n^.-s .ast ,.r K.,s A-i^.-l.-s; l.m ii..l imtil .laiii.s W. Marsha ll's -lis,-,. v.tv 
..11 111,- Am.li.-aii l:i\<-|- in lli,- f,... thills ..I III.- Si.-iia .\.-\a,la. .1 iniiarv Ul, IS'IS, .lid 
111.- ,.,-,nri-,ii,-,- ,.r t;,.|,l in falir,.riiia I., .-..ni.- si^;mli.-a r,l . 

h'roiii 1.^4S to l!):;;; ( 'jilironiia 's ^^old ])i-(i(liicl ion ninoimfcd to nearly 
Iwi) liillidii (l(.ll;irs. (.r wliicli (iiic .111(1 ;i (|iiiirtci- billion caiuc tVoni placer 
-I'avcl. 'I'Im" ratio of o-(,|,l pi-odiiccd from ]»lac<M-s 1o <;-ol(l produiMvl from 
lo.lcs issJM.u,, in III,, lullowinu- table: 



h'lili', ui ,,l„,-, r ),ii.<liirl„n, lo hnir l,n,il iirllun 
I'rr- 
I'liioil rent I'crlixl 
1S4S l<. IN.-.U 100 ivji ,,, i,(()(, 



isr.l I.. IMJO 

l.SIJl !<• ISTd 

1.S71 I.. I.SSd 

1S.SI l» ISIW) 



'.l!l I'.MM I., l'.»l()_ 
!>() IMII lo 1020. 
70 1!»L'I lu lO.'SO- 



re, I 

liO 

44 
44 



Sec. Ill (ilX)LOGY OF VhM'VAl DEPOSITS — .IKXKINS 159 

The decline in this ratio was eau.sed by tlie closing down of hydraulic 
mines In- the Sawyer Decision of 1S84 toj^ether with the C'aininetti Act 
of ^H'.)'^, as well as by the increased development of lode mining. The 
later increase of the i-atio was due to the use of the dredge, which was 
introduced in Califorjiia in 1898. 

Haley" has estimated that "In the neighborhood of $600,000,000" 
worth of gold (on the basis of the old price) is still recoverable from the 
old Tertiary channels, referring to both hydraulic and drift-mining prop- 
erties. There are undoubtedly many unaccounted-for channels, such as 
those that lie buried beneath the extensive lava flows which occur in 
the region lying between the Sierra Nevada and Klamath mountains. 
Though most of these are not today available for mining, the channels 
along the margin of this area may some clay be reached. It is conceiv- 
able, however, that the reserves in buried channels throughout the Sierra 
Nevada, workable only through underground methods, should.be reckoned 
at least in terms of hundreds of millions of dollars. 

The economic significance of the buried channel and the importance 
of its exploration should not, therefore, be slighted, for it represents a 
vast future source of gold wealth for California. The revival of the 
channel-mining industry is made still more interesting by an understand- 
ing of the detailed geologic features, the possibilities they suggest for 
certain of these buried stream courses, and the realization of the vast 
extent of the region yet to be explored. 

Since an estimate of the potential wealth of the desert placers 
depends upon further exploration and mining of them, it is not yet pos- 
sible to evaluate their place in this study. 

History of Development 

The discovery of the Tertiary channels followed shortly after the 
discovery of gold in the present stream courses. In places, remnants of 
Tertiary channels were found lying exposed high up on 'flats,' stripped 
of their volcanic covering by Pleistocene erosion. Starting from these 
flats, the miners followed the uncovered channel to the point where it was 
covered by the lava capping, the top of which formed another kind of 
'flat. ' Water was nearly always encountered, which led to the construc- 
tion of long and expensive drainage tunnels. To place these tunnels at 
the proper elevation to .serve their best purpose was the most serious prob- 
lem, for the old-timers did not have the powerful pumps which we use 
today. 

The ideas developed concerning the courses and positions of the 
ancient channels were many and varied. Misconceptions of Tertiary 
physiography led many per.sons astraj^, and millions of dollars were spent 
in vain. In spite of the millions gained, the losses were so great as to 
stamp this form of mining as hazardous in the extreme. 

It is most instructive to follow carefully the recorded history of min- 
ing in a given district and to consider its relation to the geologic condition 
of that area. The two are so closely related as to provide a guide to the 
probable history which might be expected to be found in another area if 
the geology were known, or vice versa ; the recorded history reflects what 
geologic conditions may be expected. 

13 Haley, C. S., Gold placers of California: Califurnia Min. Bur. Bull. 92, p. 5, 1923. 



160 



rLA<f;K MiNixf; lou coi.n in camfounia [Bull. 135 




Fig. 32. Old work of tlie Valclor DredRing Company in the bed of the Trinity 
River, Junction City. l!<ii( h Kmvel exposed on the opposile side of tho cjinyon show.s 
the effect of early liydraiilic jniiiing. 




Sec. TI] oEOT.or.Y of placer deposits^ — jenkins 161 

Tlie geolofile liistory and structure of the buried channels are so com- 
plex tliat tlie best engineers have been baffled by them. Frafrmentary 
benches and sep:nionts of rich frravel deposits which still rest in posi- 
tions conij^letely liidden from the surface, or even from the underground 
passages wliicli enter into the knver, main channels, afford alluring pos- 
sibilities to the geologist and geophysicist as well as to the prospector. 
A three-dimensional surface, complex and irregular in the extreme, is the 
problem to be faced. 

The key to the solution is geology, aided by aerial photography, fol- 
lowed by new geo])hysical surveying, and finally by directed prospe<-ting 
through means of the drill, shaft, incline, or tunnel. To be effective, all 
these methods should be coordinated into one unified exploration pro- 
gram. 

Classification of Placers 
Outline of Classification 

A systematic geological study of placers calls for an orderly classi- 
fication dividing them into genetic types, which indicate how they were 
first formed. The following classification is based upon the fundamental 
conditions of deposition : 

Fundaineiital clusaificatioii of iihncrs 

A. Residual placer.s or 'seam diggings.' 

B. Eluvial or 'hillside' placers, representing transitional 'creep' from residual 
deposits to stream gravels. 

C. Bajada placers, a name applied to a certain peculiar type of 'desert' or 'dry' 
placer. 

1). Stream placers (alluvial deposits), sorte<l and re-sorted, sinii>le and ci>:\- 
lescing. 

E. Glacial-stream placers, gravel deposits transitional from inoraint's. for tlie 
most p.irt valueless. 

F. Eolian placers, or local concentrations caused liy the renioxal of liglilcr nmti'- 
rials by the wind. 

G. Marine or 'beach' placers. 

Of these seven types, the ordinary stream i)lacer is by fai- tlic most 
important. All types are, however, more or less interrelated jind iiitci-- 
gradational ; they are all subject to deformation or burial, mikI tlicy m;i.\- 
be formed during any geological pei'iod. 

Most of these various types of ])lacer (lei')()sits have been well 
described and classified by Brooks," ]\lertie,'' jind others '" in tiicir studies 
of Alaskan geology. Webber" recently ])i-oposed the luime, "bttjada 
placer" for peculiar desert, or so-called 'dry' i)lacers, which he carefully 
analyzed. The concentration of gold by the agency of witid in Western 
Australia has been described by Kickard ''" and Hoover." 

"Brooks, Alfred H., The gold placers of parts of Stward 1 '. niiisula, AhisUa : TS 
Geol. Survey, Bull. 328, pp. 111-1:51), Uiits. . . . Miiu-ral icsourivs ..f .Maska. report, 
on progress of investigation.s in IIU.S : U.S. Ceol. .Siirvtv, lUill. 5111', j))). 27-;!l', r.il4. 

"^Mertie, .1. B., Jr., The occurrence of iiictallii'vrous rifposits in tlu- Yukon and 
Kuskokwim regions: U.S. (Jeol. Survey Bull. 7:'.:i. i))). ICd-lc,."), i!»2:!. 

1" Wimniler, Xorman I-i., Placer niining methods and costs in Alaska; I'.S. I!uf. 
Mines Bull. 2.59, p. 11, 1927. (Clas.silication of i)lacers.) 

" Webber, Benjamin X., Bajada placers of the arid southwest : Am. Inst. .Miii. Met. 
Eng., Tech. Pub. .588, pp. 3-1 G, 1935. 

"Rickard, T. A., The alluvial deposits of Western Australia : Am. Inst. >Iin. Met. 
Eng., Trans., vol. 28, pp. 490-.537, 1S98. 

"Hoover, H. C, The superficial alteration of Western Australian ore-deposits: 
Am. Inst. Min. Met. Eng., Trans., vol. 28, pp. 758-705, 189 8. 



162 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 



Oufcrop yy/Z-h 
■^9 ^^"^yCTS res/duaf c^epos/f 




I I Grave/ ^ sancf 
|\* 'I Ricfr p/acer 



SCALE M r££r 



Confoor /nferya/ 50 



Fig. 54. A, Diagrammatic cross-section sliowing the 
transitional stages in the development of jilacer deposits : 
First, the quartz vein ; second, disintegration at tlit outcrop 
to form a residual placer ; third, formation of eluvial i)lacer 
by 'creep' of rosiilual material down tlie hill sloi)e ; fourth, 
deposition of \vatiT-\vi)rl<ert material as alluvium, forming 
an auriferous gravel diriosit, or stream placer. />', Sketch 
map showing development of rich i)lacers broken down 
directly from the disintegration of a gold-bearing vein ; 
after Lindyren, Mineral Deposits. 



General Statement 

111 valuatiiif^ a placer, one of the first considerations should be the 
detenu illation of how it was formed. It is reeoininended, therefore, tliat 
the exploration entrineer should classify frenetically each gravel deposit 
to be prospected. This calls for an understanding of the historical 
geology of the region and of the processes which have been responsible 
for the formation of the deposit, as well as how it came to be preserved 
or modified from its original form. The actual sampling of a deposit is 
carried on in a much more intelligent and satisfactory manner when a 
clear understanding of the geologic set-up has been acquired. 



See. TI] fii:OLO(;Y OF PLACER DEPOSITS — JENKINS 163 

Characteristics of the Principal Types of Placers 
Residual Placers 

In order that ^olcl may become released from its orij^inal source in 
bedrock, the encasing material must be broken down. This is most effec- 
tively done by lon«i-continued surface weathering. Disintegration is 
accomplished by persistent and powerful geologic agents, which effect the 
mechanical breaking-down of the rock and the chemical decay of the 
minerals. 

The surface portion of a gold-bearing orebody will become enriched 
during this process of rock disintegration, because some of the softer and 
more soluble parts of the rock are carried away by erosion, leaving the 
remaining portion of higher tenor. The name ' residual placer ' is applied 
to this type of deposit. After the residual portion is mined away by com- 
paratively inexpensive methods, the harder mineralized rock is encoun- 
tered, and the mining methods must be changed to accommodate another 
type of deposit, i.e., the lode. 

The so-called 'seam diggings' are in weathered, gold-bearing quartz 
stringers, occurring along fracture zones of disintegrated schists. 

Eluvial Placers 

After gold is released from its original bedrock encasement through 
agents of rock decay and weathering, the whole weathered mass may 
'creep' dovni the hillside (in some regions partly because of frost heav- 
ing) and may finally be washed down rivulets into gulleys. Lindgren ** 
states : 

"When the outcrops of gold-bearing veins are decomposed a gradual concentration 
of the gold follows, either directly over the primary deposits or on the gentle slopes 
immediately below. The vein when located on a hill.side bends over and disintegration 
breaks up the rocks and the quartz, the latter as a rule yielding much more slowly than 
the rocks ; the less resistant minerals weather into limonite, kaolin, and soluble salts. 
The volume is greatly reduced, with accompanying gold concentration. The auriferous 
sulphides yield native gold, hydroxide of iron, and soluble salts. Some solution and 
redeposition of gold doubtless take place whenever the solutions contain free chlorine. 
The final result is n loose, ferruginous detritus, easily washed and containing easily 
recovered gold. This gold consists of grains of rough and irregular form and has a 
fineness but slightly greater than that of the gold in the primary vein." 

On its way down the hillside, gold is sometimes concentrated in suf- 
ficient amount to warrant mining. Such deposits are classified as eluvial 
placers. They are transitional between residual and stream, or alluvial, 
deposits. 

There have been a number of residual and eluvial gold deposits 
mined in both the Sierra Nevada and Klamath Mountains ; for example, 
the 'seam diggings' of Georgia Slides,^ El Dorado County, and Scott 
Bar,^ Siskiyou County. 

Stream Placers 

By far the most important type of placer is the ordinary alluvial 
gravel or stream placer. So far, it has been the source of most of the 
placer gold mined ; but now its supply is nearing depletion, save for 
values remaining in those ancient channels which lie deeply buried 
beneath a cover of lava or rock debris. 

«> Lindgren, W^., Mineral deposits, p. 213, McGraw-Hill Book Co., 1919. 

^1 Logan, C. A., Mother Lode gold belt of California : California Div. Mines Bull. 
108, pp. 43-44, 1935. • 

22 Logan, C. A., Siskiyou County : California Min. Bur., Mining in California. State 
Mineralogist's Rept. 21, p. 474, 1925. 



164 



PLACER .MIXING FOR COLD IN CALIFORNIA 



[Bull. 135 




Fig. '>'>. Quartz Hill mine, Scott River, Siskiyou Cour.ty. DisenteKrated material 
formed in the upper part of gold-bearinK veins, by residual weatherins, has been re- 
moved by hydraulic mining. Note the terrace-like profile of the hill, indicating tliat an 
older, less rugged surface existed at the time this deep weathering took place. Uplifting 
of the region entrenched the drainage, and much of the gold released by weathering was 
washed by Pleistocene erosion into Scott Hiver where rich gravel bars have been mined. 




Sec. II] GEOLOGY or PLACER DEPOSITS — JENKINS 165 

Deposits by streams include those of both present and ancient times, 
whether the}' form well-defined channels or are left merely as benches. 
Stream placers consist of sands and jiravels sorted by the action of run- 
ninjr water. If they have underjrone two or more periods of erosion, and 
liave been re-sorted, the result will in ail probability be a comparatively 
high de<iree of concentration of the heavier mineral j^ains. 

Quoting from Mertie :" 

"All l)oiK-h placer.s, when fir.st laid down, were stream placers similar to those of 
the jiresent stream valleys. In the course of time the stream gravels, if not reworketl 
by later erosion, may he left as terraces or benches on the sides of the valley, if the 
local base-level is lowered and the stream continues to cut down its channel. Such 
deposits constitute the so-called bench gravels. On the other hand, if the regional or 
local l)ase-level is raised, the original placer may be deeply buried and a second or later 
placer deposit may be laid down above it. * * * If the local base-level remains 
l)ractic.illy stationary for a very long period, a condition seldom realized, ancient and 
recent placers may form a perfectly continuous deposit in a long valley, for the deposi- 
tion of a gold placer is known to occur at that point in a valley where the stream action 
changes fmm erosion to alluviation, and such deposits are therefore formed progres- 
sively ni)stream. 

"Where several parallel and contiguous streams that are forming placers emerge 
from their valleys upon an open plain, perhaps into some wide valley floor, a continuous 
or coalesc-ing placer may be formed along the front of the hills. "If the streams empty 
info some lake or estuary, a delta placer, genetically the same but perhaps different in 
some minor respects, may be formed. Manifestly such compound placers may be 
formed i>y either present or ancient streams and may be elevated or buried in the same 
w.iy as simple stream placers." 

In order to understand thoroughly the subject of stream placers, 
streams tliemselves must be studied in regard to their habit, history, and 
charHcter. The effects of existing and changing climates, the relation to 
surrounding geologic conditions, and the effect of movements of the earth 
must also be considered. A special chapter in this report has therefore 
beeji devoted to a brief outline of the fundamental geologic features of 
streams. 

Glacial-Stream Placers 

It is a frequent fallacy of the placer miner to attribute the deposition 
of gold-bearing gravels to the action of glaciers. Contrary to such a 
belief, glaciers do not concentrate minerals; the streams issuing from 
melting ice, however, may be effective enough in sorting debris to cause 
placers to be formed under certain especially favorable conditions. In 
California, glaciers occurred througliout the high Sierra during the Pleis- 
tocene, but in Tertiary times they were wholly lacking. The Pleistocene 
streams cut through the earlier channels, robbing them of much of their 
gold. 

Quoting from Blackwelder : " 

"Since it is the habit of a ^laciei- to scrape oK loose debris and soil but not to 
.sort it at all, ice is wholly ineffective as an agency of concentration for metals. Gold 
derive<l from the outcrops of small veins is thus mixed with large masses of barren 
earth. Attempts to mine gold in glacial moraines, where bits of rich but widely scat- 
tered float have been found, are for that reason foredoomed to failure. 

"If a glacier advances down a valley which already contains gold-bearing river 
gravel, it is apt to gouge out the entire mass, mix it with much other debris and deposit 
it later as useless till. Under some circumstances, hinvever, it merely slides over the 
gravel and buries it with till without (lisi\irliiiii; it. 



^Op. cit., pi>r 161-162. 

2« Blackwelder, Eliot, Glacial ami ;iss(Kiat>-(l stitain ikpi.siis nf the Sierra Nevada : 
California Div. Mines, Mining in California, State .Mineralngistb Kept. 28, pp. 309-310, 
1932. 



166 



PLACER MINING FOR GOLD IN CALIFORNIA 



Bull. 135 




57. Hyilraulicking a hijih bench-gravel depo.sit of the Trinity River, near Us 
confluence with the South Fork. Location : Salyer mines, pit No. .'i. 



"On the other hand, the .streams horn of ghieiers or sh>\vly con.siiininK their 
moraines have the power to winnow the particles of rock and mineral matter according 
to size and heaviness. Such streams may form Kold placer deposits in the well-knowti 
way hy churning the load they carry and allowing the heavy minerals to sink to the 
bedrock. Placers may therefore be found in the deposits of jclacial rivers if there are 
gold veins exposed in the fjlaciated area upstream. Nearly all the gravel which has 
been dredged for gold along the foothills of the Sierra Nevada was deposited l)y rivers 
derived in part from glaciers along the crest of the range, but most of the gold was 
probably picked up in the lower courses of such rivers. Since glacial rivers choko 
themselves and Ixiild up their channels progre.ssively, their deposits are likely to he 
thicker and not so well concentrated as those of the more normal graded rivers which 
are not a.s.sociated with glaciers." 

A few gold-bearing deposits in re-worked glacial till may be found 
along the eastern front of the Sierra Nevada, as, for example, in the 
region just north of Mono Lake on the road to Bridgeport. 

Bajada Placers 

The name 'bajada' was first used by Tolnian "" for confluent alluvial 
fans along the base of a mountain range. Recently Webber "" named and 
described the bajada type of placer deposit as follows : 

"Bajada is the Spanish term for slope and is used locally in the Southwest to 
indicate the lower slope of a mountiiin range, the portion consisting of rock debris and 
standing at a much lower angle than the rock .slope of the range proper. • * ♦ 

"The total production of gold from l)ajada placers in the southwestern Inited 
States is neces.sarily .small, probably not over ten million dollars. ♦ ♦ • 

"Most all bajada placer gravels are Quaternary and the larger part are recent. 
* • * 

"The genesis of a bajada placer is basically similar to that of a stream placer 
except as it is conditioned by the climate and topography of the arid region in which 
the placer occurs. ♦ * • 

"Erosion, transportati<jn and deposition in a region of extreme aridity present 
some phenomena not encountered in more humid areas. Practically all the work «>f 
running water is strongly conditioned by aridity. ♦ • ♦ 



=''' Tolnian, C. ¥".. Erosion and deposition in southern Arizona bolson region: Jour. 
Geology, vol. 17, pp. 136-163, 1909. 

"Webber, B. N., op. cit., excerpts from pp. 3, 4, 6, 8, 10, 11. 



Sec. II] GEOLOGY OF PLACER DEPOSITS — .IF.XKIXS 1()7 



'■< 


^^ 


1 


^ 


^Ig^^S*^ 



Fig. 58. Cross-section of a Kold-bearing desert stream vallty ( .Manliattan, 
Nevada), showing the result.s of several periods of stream deposition from the old- 
est (1) to the youngest (6). Aiier Ferguson, U. S. (leol. Survey Hull. 7 2.1. 

"Rock-floored canyons through which rock fra^tnent-s arc moved l)y infrequent 
torrential floods should con.stitute excellent pel)l)lp mills for the further reduction of the 
material, hut the amoiint of attrition accomplished seems to lie .sliRht, as fracmeuts, 
lar^e or small, on the hajada slope are decidedly anyidar and show little effect of attri- 
tion. * * * Prohahly a small percentage of the ^(dd is freed durinj,' this phase of 
the movement of gravel. The gradient of the.se intermont drainage channels is too high 
to permit lodgment of the finer gravel. When a small amount of gravel is temporarily 
lodged in one of these channels, the deposit displays most of the characteristics of 
stream gravel. 

"As dehris reaches the hajada .slope a rapid diminution in volume of water due to 
seepage and an extreme decrease in the grad(^ of channel causes deposition of dehri.s, 
and either (1) an alluvial fan or (2) a gravel-mantled pediment may he formed. If 
detritus is supplied to a hajada slope much faster than it can be removed, an alluvial 
fan is the result. * * * jf i.,,(.k dehri.s is supplied to the hajada slope in consider- 
able volume but not in excess of the (piantity capable of transference to the center of 
the basin by the existing agencies, a gravel-mantle pediment results. * * * 

"The bulk of the gold that has been released from its matrix on the journey from 
lode outcrop to hajada slope is deposited on the hajada slope close to the mountain 
range. The gold is dropped along the contact of the basin fill and bedrock ; this is 
referred to hereafter as the lag line and is coincident with the line of contact of hajada 
gravels lying at a low angle and the rock slopes of the range standing at a high angle. 

"The heaviest deposition of gold is on bedrock at the lag line, and since the lag 
line is moving in the direction of the crest of the range, values on bedrock may be dis- 
tributed over a large area of which the longest dimension is parallel to the foot of the 
range. Because bulk concentration does not operate as in a river channel, and a cer- 
tain percentage of the gold is still locked in fragments of matrix, to be partly released 
by further disintegration on the i)ajada slope, there is a strong tendency for less gold 
to reach betlrock and for more to remain erratically distributed throughout the detritus 
than in the ca.se of stream gravels." 

There are probably many examples of typical bajada placers in the 
Mojave Desert and Great Basin regions of California, but recognition of 
them as such has not yet reached publication. Reconcentrations from 
former gold-bearing streams in the Mojave Desert have been described 
by Hulin '"' and dry placers in .southern California have been listed by 
►Sampson.^ 

Eolian Placers 

Webber ^' states that : "Bajada placers usually show an appreciable 
and even considerable enrichment on the surface due to removal of lighter 
material by wind and sheet floods." This applies to some of the dry 

2" Op. cit. 

^ Sampson, R. J., I'lacers of southern California : California L)i\-. Mines, Alining in 
California, State Mineralogist's Rept. 28, supplement, pp. 245-255, in;;2. 
»Op. cit., p. 15. 



KiS 



I'LACCK MININC lOK COLO IN' fAr-II'ORNIA [Bllll.l:}3 




'I'lacer mining in tlie beach sands at Santa Cruz, California, 1933, 



placers of California, though no commercial eolian gold deposits such as 
those mined in Australia, previously referred to, are known in this state. 

Wind action, however, is responsible for the removal of large 
amounts of fine detritus in the desert. The process involved has been 
called 'deflation' and its results described by Blackwelder." It is quite 
likely that it will be found to play an important part in the surface con- 
centration of desert placers. 

Spurr" described "auriferous sand dunes" in the Nevada desert 
seven miles south of Silver Peak, 18 miles from the California boundary 
line. 

Beach Placers 

Concentrations of heavy minerals occur in various places along the 
Pacific Coast as a result of the action of shoie currents and waves, which 
tend to sort and distribute the materials broken down from the sea cliffs 
or washed into the sea by streams. The heavy minerals consist for the 
most part of magnetite, chromite, ilmenite, monazite, and zircon, with 
occasional fine particles of gold and platinum. Beach placers are of two 
kinds, (a) present beaches and (b) ancient beaches, ^n elevated coast 
line is often found overlaid with terrace gravels which ^'ere deposited at 
a time when the coastline was depressed. The beach placers of economic 
importance are those thatTiave been reconcentrated over and over again^ 

Excellent descriptions of the geologic processes involved may %c 
found in reports on beach placers of Nome,"" Alaska, and of the coast 

*• Blackwelder, Eliot, The lowering of playas by deflation: Am. Jour. Sci., vol. 21, 
r.th ser., pp. 140-144, 1931. 

3' Spurr, J. K., Ore deposits of the Silver Peak quadrangle : U.S. Geol. Survey Prof. 
Paper 55, pp. 96, 97, 1900. 

»» Mofflt, Fred H., Geology of the Nome and Grand Central quadrangles, Alaska : 
U.S. Geol. Survey Pull. 533, pp. 109-123, 1913. 



Sec. II] 



GEOLOGY OF PLACER DEPOSITS — JENKINS 



169 















is^^^r-.'^^^- -i^#^; j^^ 





.•-'-V\ 



-« orfsf<ore --->^ 

S«« /AX^L_ 


» Shora ->— < Shora - - - - i— - iTojs/ _Jq 


^X-<^', ■' , ; ^^^^y-^ \tr,s,on p'Bffi>rm 


-^ '■' ^ ^s/'a'-'-"' -^Htgh-hde shore /,r,e. 



Fig. 60. A. Diagrammatic cross-section illustrating the formation of beach 
placers in Alaska : njter CoWier aii<l Hess. U. S. Geol. Surrej/ Bull. S28. B. Cro.ss- 
.section of a tj'pical beach placer (Oregon) ; nftrr Pardee, U. H. Gcol. Survey Cire. 8. 
C, Diagrammatic cross-section of a coast, showing shore zones in an advanced stage of 
development; after Johnson; see Pardee, U. S. Gcol. Suri^eij Circ. X, UU.',. 



of Oref^on^ and California.^' In discussing the origin of the gold in 
the Oregon beach placers, Pardee ^ saj's : 

"Some of the niiuens believe that the jjold of the he.iclies comes up out of the sea. 
an idea suggested by the fact that after a storm a formerly l)arren stretch may be found 
to be gold-bearing. This notion is true so far as the immediate source of .some of the 
gold is concerned. Materials composing the foreshore are carried out in the offshore 
zone at one time and returned to the beach at another. In the, process a shift up or 
down the coast may occur. * * * Soundings of the Coast and Geodetic Survey 
show black sand to occur in the offshore zone at the present time. Gold and other 
minerals are <loubtless i)resent also. * * * it^or the beaches that border retreating 
shores, however, the nu)st of the gold and other minerals come directly from the-rocks 
that are being eroded by the waves." 

The economic possibilities of mining the black sands of the California 
coast for their gold content liave long been discussed.'" Although gold 
and platinum have been the only minerals in the black sands which have 
been mined at a profit, much study has been given to the possible economic 
value of the other constituents." 

Gold-bearing gravels of marine origin occur in the Chico (Upper 
Cretaceous) sediments of northern California. That they are marine in 

■" Pardee, J. T., Peach placers of the Oregon c<ja.st : I'.S. f leol. Survey, Circ. 8, 1934. 

=*' Hornor, R. P., Notes on the black sand deposits of southern Oregon and northern 
California: U.S. Bur. Mines Bull. 19(i, 1918. 

« Pardee, J. T., op. cit., pp. 29, ZO. 

=>» Edman, J. A., The auriferous black .sands of California : California Min. Bur. 
Bull. 4.5, 1909. 

'■^ Dav, D. T., and Richards, R. H., Black sands of the Pacific slope : Mineral 
Resources U.S., 1905. pp. 1175-1258, 1907. 



170 



PLAfKR MININT! FOR HOLD IX CALIFORNIA 



[Bull, i;}.') 




I'h; ',1 AimI.-ii. 'r^. 1. 1)1. -w:. Mi' .iipI I. r. ■.■.!,. >. .- i ly- volcanio-ash beds. 
M:itfij;il iif this sort oiiio coxi loit most <il tlic iiidtliUi licit of the northern Sierra 
Nevaila. Location : 2 miles soutli of KniBlits Ferry, Tuolumne County. 

()ri«riii and not fluvial is shown by tlieir content of abundant fossil sea- 
shells, as well as by the character of their strata. They were formerly 
wron<rly classed as "the gravel-filled channel of a IMesozoic river.'"* 
Gold-bearinjr jrravels have also been reported from marine sediments of 
the Lower Cretaceous of northern California. 

Since the gravels of the Eocene rivers of the Sierra Nevada were 
richly gold-bearing, it is to be expected that some of the gold reached the 
sea. The sedimentary deposits of this Eocene sea are known as the lone 
formation. They occur along the "western foot of the Sierra Nevada. 

Lindgren says : "' 

"At the motitli of the rivers wliich descended from tlie IVrtiary Sierru Nevad.i 
extensive delta deposits were jiecuiniilated, and it is thus diflicult in many places to 
draw any exact line lietween the lone formation and the river gravels proper. The 
gravels in the formation are locally auriferous, though generally poor, hecause spread 
over large areas." 

The deposits contain (juartz gravels aiul finely divided quartz grains; 
they are closely connei'ted with the oldest river-channel deposits; they 
occur along the extreme western foot of the Sierra Nevada. Therefore, 
as stated by Allen,*" the lone sediments 

"* * * indicate delbi deposits formed at the mouths of many westward-flowing 
streams. The presence of marine fossils in the upper part of the lone formation shows 
that they accumulated on the shores of an Eocene sea." 

The processes involved in the distribution and concentration of gold 
in the marine strata of both the Cretaceous and Eocene formations have 
never been carefully studied. If these marine and delta placer deposits 
have any particular economic significance, it certainly has not been ade- 
(luately demonstrated. 

^ Dunn, R. h-, Auriferous conKlomerate in California : California Min. Bur., State 
AlineraloBisfs Uept. 12, pp. 4r)!(-471, map p. 461, 1894. 

" Lindgren, W'., op. cit.. Tertiary gravels, p. 24. 

«" Allen, Victor T., The lone formation of California : Univ. California, Dept. Geol. 
Scl. Bull., vol. 18, p. 348, 1929. 



See. IT] GEOLOGY of placer deposits — JENKINS 171 

Preservation of Placers 

Placers are preserved if soniethiiif; keeps them from beinj? eroded 
away. Since streams are continually changing their positions, fragments 
of their deposits are often left isolated. Tn cutting a deeper channel, a 
stream leaves 'benches' or 'terraces' at different intervals along its valley 
sides; but erosion tends to desti-oy them, unless they are protected in 
some way. 

Burial is the most effective way in which a placer may be preserved. 
The name 'buried channel' has often been restricted to streams covered 
deeply by lavas, mud-flows, ash-falls, etc., all of which were very common 
during the Tertiary period in the Sierra Nevada. There are, however, 
other means by which burial may be effected. 

1. By eoveriiiK with liind.slide material. (An example occurs in Canyon Creek, 
Trinity County.) 

2. By covering with travel, cau.sed by the fanlting-down of a part of the river 
system. (Examples are l)elieved to occnr alonp; the Klamath, Trinity, and 
some of the larjcer rivers of the Sierra Nevada.) 

3. By covering with like deposits. (Many of the l)uried Tertiary channels were 
covered first by lake sediments, called 'pipe-clay,' before lava or mudflows 
poured over them.) 

4. By coverinR with gravels when the stream is choked. (Examples are common 
along stream systems.) 

5. By covering with gravel when the stream course is lowered below the general 
base-level of erosion. (Examples of this case are found along the western 
foot of the Sierra Nevada.) 

6. By covering of the bedrock surface of down-faulted blocks (graben) by .sedi- 
ments of various sorts. (Many examples, especially in the Great Ba.sin and 
Mojave Desert regions.) 

7. By covering of older stream courses with alluvial fan material, as conditions 
favorable to stream existence fail. (Many examples in the Great Basin and 
Mojave Desert regions.) 

8. By covering with glacial till. (Examples may be looked for in the glaciated 
areas of the Sierra Nevada.) 

9. By covering of beach placers with marine sediments as the fluctuating coast 
is submerged, but later elevated. (Such as the present elevated beach placers 
which are in places covered with other marine se<liments.) 

10. By covering of one geologic formation with another, through the processes of 
earth deformation and thrust-faulting. (In a geologically active region such 
as California, examples of this case might very well i»e found.) 

11. By submergence of river canyons ^^ to great depth beneath the ocean. (Off 
the coast of California many submarine channels have been discovered and 
mapped by the V. S. Coast and Geodetic Survey. One extends over 75 miles 
from the shore and attains a depth greater than 10,000 feet. These channels 
are too deep, therefore, to explore for placer gold. A reported recent project 
to operate a sea-going gohl dredge would probably have to do only with off- 
shore marine deposits and not submerged stream placers.) 

To find gold-bearing stream chainiels, buried and preserved in such 
a manner that they may be profitably mined, is the challenge to the 
exploration geologist. 

Modification of Placer Deposits 

Placer deposits may be greatly modified in form and structure by 
earth deformation. The gravel content may also become firmly cemented 

*• Davidson, George, The submerged valleys of the coast of California : California 
Acad. Sci., Proc. (3) vol. 1, no. 2, 189 7. 

Reed, Ralph D., Geology of California (with references), p. 3, Am. A.ssoc. Petro- 
leum Geologists, 1933. 

Shepard, Francis P., Investigation of California submarine canyons (abstract) : 
Geol. Soc. America Proc. 1933, pp. 107-108, 1934. 



172 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 




Fig. 62. Diagram showing a down-tlroppefl fault Mock (grahen) bttween tun 
upLifted fault blocks. Krosion cover.s the one with materials derived from tht- othfr.K. 
Streams cut in bedrock iirior to faulting ma\ thus be buried under the alluvium of 
the graben. After Davifi. Stale Miu(r<tl<)tji.st'.i Itrpt. >U. ' 










l^ 



Via. <;.T. Ideal sketch showing bow a 
landsliiic may dam up a iiKnintain valliy to 
form a lakf. Silt, sand, and giavils deposited 
in and on the edge of this lake will rnvi r tbv 
stream gravels in its bottom. .1/^/- Dm is. 
Slate MiiicialiKiisfii Uriit. .i'.i. 



Sec. TI] r.EOLooY ok plackr i)i:r()S!Ts — -.ikxkixs 173 

by intci-stitial deposition of mineral inattci-, such as by lime and iron ear- 
bonate. or silica, tliron-zli tlie action of infiltratinti' solutions. The older 
the ])lacer, the more apt it i.s to have been modified in these ways from its 
orijiinal form and attitude. 

The re«»ional tilt of the Sierra Nevada has increased the gradient of 
the Tertiary channels " (where tliey lie in the direction of the tilt) from 
20 or 30 feet to the mile to twice, three times, or even several times that 
amount. Locally, tiltinji" has been even {greater. Tn places where the 
ancient channels lie \n opposite (lire(;tion to the tilt the ori<iinal !,n-adient 
may have been reversed. Often steep tilting' is accompanied by local 
faulting: of a few feet to .several hundred feet, (ienerally the down- 
throw is on the east side of the fault plane. Tn form, this is a replica of 
the action which took place and still is takinjr place alon<>- the eastern 
escarpment of the Sierra Nevada. Such displacements and chanj^es in 
channel-firadient as well as in actual position of the channel, are impor- 
tant factors which greatly influence mining' procedure. They should be 
nnder.stood so far as .surface data will i)ermit, before actual mining is 
started in a given area. 

In the Mojave Desert and Great Basin region, faulting and tilting 
liave been extremely active, greatly affecting streams antedating late 
Tertiar}- and early Quaternary periods. 

The tiow of ground w^ater through stream gravels, the former chan- 
nels of which have been blocked, cut off, tilted, or folded by earth move- 
ments, is a factor of considerable consequence when it comes to mining 
such placers. ^5l yv '. <-^ " 

Gold in Placers < •" 

Original Source of Gold ^ ,, 

The particles of gold found in placers originally came from veins 
and other mineralized zones in bedrock, irqm which they were released 
through surface weathering and disirttfegration of- the rock matrix. ■^^_' 
Though the original source may not in every case have been a deposit 
which could today be mined at a -profit, the richer placers usually indicate 
a comparatively rich source. ^A long period of deep weathering, result- 
ing in separation and release of large quantities of gold from the bedrock, 
followed by a more active period of erosion, generally due to uplift, is an 
ideal condition for gold to be swept into stream channels and there to be 
concentrated into rich placers. Still richer deposits may be formed 
through reconcentration from older gold-bearing gravels. 

These are the most important geologic conditions which have been 
found to exist in the various gold belts of the world, and particularly in 
the Sierra Nevada of California. 

For the most part, the original source of gold is not far from the 
place where it was first deposited after being carried by running water. 
This is certainly true in both the Sierra Nevada and Klamath Mountains. 
The streams,^|lo>ving through regions of metamorphic and intrusive igne- 
ous rocks threaded throughout by gold-bearing veins, were found by the 
early miners to contain auriferous gravels. But the more recent streams 
which have had only barren lavas to pass over, as in the volcanic covered 
area between the Sierra and Klamath regions, have proved to be barren. 

Lindgren " states : 

*2L,indgren, W., op. cit., Prof. Paper 73, pi. X, Profiles along Tertiary channels of 
the Sien-a Nevada. 

« Lindgren, W., Mineral deposits, p. 213, McGraw-Hill Book Company, 1919. 



174 PLACER MINING FOR GOLD IN CALIFORNIA | llllU. 13.') 

"Tho Kroat majority of roUI placers liavo Ikmmi dcrivod fi<>tn tlif wcathfriti},' and 
disintegration of adrifermis veins, lodes, shear zones, or more irre;;idar replacement 
deposits. • • * In many regions (he rocks contain altnndant joints, seams, or 
small veins in which the gold has been deposited with quartz. ♦ * * It is often 
stated that gold is distributed as fine particles in .schists and massive rocks and that 
placer gold in certain districts is derived from this source. Most of these statements 
are not supported by evidence, though it is not denied that gold may in rare instances 
be distributed in this manner." 

Release of Gold from Bedrock 

Without some wide.spread process of release from the quartz veins 
and rocks — vaults in which the metal was orioinally firmly held — gold 
particles could not have escaped to be transported as such by running 
water. Tiierefore, extensive rock weathering and decay over a long 
period of time is a primary factor of extreme importance. It has per- 
mitted the original source to contribute gold particles, large and small, 
to placer accumulations. The same gedlogic processes which form 
residual and eluvial or 'hillside' concentrations of commercial merit 
operate in the general release of gold from bedrock. - , 

The factors of prime importance in weathering are solution, 
changes of temperature, depth of water-table and therefore depth of 
oxidation, action of rain, effect of gravity, growth of vegetation, nature 
and composition of material acted upon, and degree of topographic 
relief. Rock weathering, especially complete disintegration down to 
the^water-table, rather than deep disintegration, is often more favored 
by tropical climates. This, however, is only one factor, and large areas 
of deep secular weathering are found in the north, in such places as 
Alaska, where placers are abundant. 

The processes which take place in the separation of gold from 
bedrock are described in detail by Brooks,^'* who says-., 

"The breaking down of the rock and the accompanying chemical changes of the 
constituent materials set free the gold, one of the relatively indestructible minerals, 
and this becomes intermingled with the other insoluble material. Clay dominates in 
the residual raa.ss, but if the parent rock contained quartz, this, too, usually remains, 
being probably the most refractory of all the common minerals toward purely chem- 
ical agencies. Mineralized vein quartz very commonly carries easily decomposed 
minerals, such as pyrites, and is therefore readily broken up, allowing the insoluble 
ingredients of the ore body, such as gold, to be set free. This process is hastened 
by purely physical agencies, such as frost and changes of temperature, which break 
ui» the insoluide rock constituents. ♦ * * 

"As a rule, the changes in a rock mass brouglit about by weathering result in 
a very material reduction in its bulk.*" The loss of material by weathering among 
siliceous crystalline rocks, according to Merrill," amounts to more than 50 per' cent, 
and in the purer forms of limestone it may reach as high as 91) per cent. Pumpelly"' 
has estimated that in the limestone areas of the Ozark Mountains the residual 
material represents only from 2 to 9 per cent of the original rock mass. Such 
reductions in volume necessarily result in more or less concentration of any insoluble 
material that may have been disseminated in the parent rock. This concentration 
will be materially greater in the case of substances of high specific gravity, such as 
gold, than in that of the lighter minerals, for the former will have a constant 
tendency to .settle to the bottom of the loose material. On declivities gravity will 
accelerate the process and help to sort the material, producing in some places a rough 



** Brooks, Alfred H., The gold'placers of parts of Seward Peninsula, Alaska : U.S. 
Geol. Survey Hull. 328, pp. 125-127, 1908. 

'' Merrill has shown that in certain changes by hydration there is an increase in 
bulk. He estimated that in the conver.sion of granite into soil (District of Columbia) 
there had been an increase in volume amounting to 88 percent. Compare Merrill, G. P., 
Principles of rock weathering : Jour. (Jeology, vol. 4, p. 718, 1896. 

' Merrill, G. P., Rocks, rock weathering, and soils, p. 2.34, New York, 1897. 

•• Pumpelly, Raphael, The relation of secular rock disintegration to loess, glacial 
drift, and rock basins : Am. Jour. Scl., 3d ser., vol. 17, p. 136, 1879. 



Sec. II] GEOLOGY OF PLACER DEPOSITS JENKINS 175 

strntificntion." This is a sociilar process and will pntcoed as loiij; as the rocks continue 
to disintegrate. * * * 

"It is evident that the effectiveness of all these agencies is proportional to the 
length of time in which they are operative. A laud mass must remain stable 
relative to sea level, for a long period of time to permit the accumulation of any 
considerable amount of residual material. Uplifts bring about renewed activities of 
the watercourses, and the residual mantle is quickly removed by erosion. It is evident 
that the conditions that are most favorable to the accumulation of residual material 
are those in which the land ma.ss is at or near ba.se-lev<'l when erosion is reduced to 
a minimum." 

It seems that topographic and climatic conditions which existed 
during the Eocene period in tlie Sierra Nevada Avere ver}^ favorable for 
the release of gold. Rejuvenated drainage at the close of the period 
swept the innnense quantities of gold, freed from the enclosing hard 
matrix into the early Tertiary stream channels ; and these, soon after, 
became buried and preserved by lake sediments, ma.sses of gravel, cobble- 
wash, volcanic ash, breccia, and lava flows. 

Associated Minerals 

Mineral grains that are very heavy and resistant to mechanical 
and chemical destruction accompany the gold in placers. The so-called 
'black sands,' generally made up principally of magnetite, are well- 
known to the miner. A long list of the minerals found in sluice-box 
concentrates is recorded by the United States Bureau of Mines.^^' 
Besides magnetite, there are found titanium minerals (ilmenite and 
rutile), garnet, zircon, hematite, chromite, olivine, epidote, pyrite, 
monazite, limonite, platinum, osmiridium, cinnabar, tungsten minerals 
(wolframite and scheelite), cassiterite, corundum, diamonds, galena, 
as well as quicl^ilver, amalgam, metallic copper, bird-shot, bullets, hob- 
nails, penknives, watches, and nails. 

Buried deeply in the gravels of the modern Feather River was 
once found (and someone thought it was an ancient fossil) the remains 
of a mule's hind leg wuth hoof and iron shoe nailed to it. What may 
be found in some of the placers of today may not, therefore, be repre- 
sentative of what was deposited by the more ancient streams. 

The presence of quantities of magnetite associated with extremely 
fine gold particles, makes a difficult metallurgical problem. To the 
geophysicist, however, the presence of any minerals having a strong 
effect on the magnetometer is a godsend to effective exploration. 

The determination of heavy minerals and their approximate relative 
percentage has been extensively iLsed in subsurface correlation^^ of 
sedimentary beds in the oil fields, and tables have been developed for use 
in determining these minerals.'*^ The same method of research could 
well be applied to the tracing of channels. Though it has not yet been 
given consideration in California, this interesting field is open for study, 
with a well-developed technique^^ available. 

e Kerr, W. C, The gold gravels of North Carolina, their structure and origin : Am. 
Inst. Min. Eng., Trans., vol. 8, pp. 461-462, 1879-80. 

<=* Gardner, E. D., and Johnson, C. H., Placer mining in the Western United States. 
Part I, General information : U. S, Bur. Mines, Inf. Giro. 6786, pp. 15-20, Sept. 1934. 

*« Tickell, F. G., The correlative value of the heavy minerals: Am. Assoc. Petro- 
leum Geologists, Bull. 8, pp. 158-168, 1924. 

" Tickell, F. G., The examination of fragmental rocks, Stanford University Press, 
1931. 

**Raeburn, C, and Milner, H. B., Alluvial prospecting, the technical investigation 
of economic alluvial mineral*, D. Van Nostrand Co., 1927. 



176 



PLACER MIXIXG TOR COLD IX (•ALlFnRXL\ 



Bull. 13i 




Fig. G4. SUetoh map of an early Tertiary channel 
and its delta in the Kocene (lone) sea. The crosses 
indicate where llie gold has heen mined in the channel — 
on a bend in the stream, and at the iioint where a tribu- 
tary entered. Finely divided gold particles occur inter- 
bedded in lenses of quartz pebbles and sand lying above 
clay layers (false bedrock). 




i\\WmPm\r'^/~i\\\^- ' ' ■! ,\^' '/n\v'' ^^/mJ^ 



'/i!\\v/^/| iV 




Fig. 65. Diagram to illustrate the course of a river, indicating where gold 
particles are most likely to become concentrated. After Spurr, U. S. Geol. Survey 
18th Ann. Rept., 1898. 



Sec. II] 



GEOLOGY OF PLACER DEPOSITS — JENKINS 











^ _^ z^- j^: S^ 



Fig. 66. i4. Diagrammatic cross-section showing the four principal ei)ochs of 
Tertiary gravel deposition in the Sierra Nevada. The deep gravels, a, represent 
Eocene ; b to d are successively younger and probably represent Miocene stages 
for the most part. The rhyolite i^eriod is representid by c and the andesite by d. 
B, Diagram showing deposits in the Deep Blue lead, Placerville ; the older channel 
and benches of the inter-rhyolitic epoch are represented by a; rhyolite tuff, h; 
andesite cobble, c, andesite tuff-breccia, d; after Lindgren, U. 8. Geol. Survey 
Prof. Paper 7 J. 







FiQ. 67. A, Diagram showing the place of greatest erosion on the bend of a 
river. B, Diagram to show positions of pressure and suction eddies in a river ; gold 
is more likely to be deposited in the suction eddy than in the pressure eddy. C, Diagram 
to show how a suction eddy is formed in a river; after Thomas and Watt; see Ries and 
Wataon, Engineering Geology. 



178 I-LACKR MININC lOU COM) IN ( Al.l l( »I{M A |r.u11.l:^'> 

The soui-fc (»f the iniiu'i-;il.s dopiisitcd jiiid associiitt'd with the '^o\d 
partiek's lies in tlie rocks over which the stream has flowed. The source 
(»f chroiiiite. i)latiiunii, and diamonds is <renerally attrihuted to helts of 
ser|)entine and irlated ultra-basic i^Mieous rocks, while <,Mruet, ilmenite 
ami ma«rnetite miyfht come from metamorpliic rocks, and mona/it<>, 
zii-con. cassitcrite, wolframite, and scheelite would probably have their 
.soui'cc in «rranite pe;zmatites. 
Transportation, Deposition, and Retention 

The pi-ocesses of transportation and deposition of ^old in a stream 
ai"e apll\' stated by JJrooks:''' 

••'I'lic Inoisiiniliii;; IM.wci- ,<( :i slic;mi is .l.'i.riKlciil nil its vrlucily. which is ;i 
v.iri.iiit (Irininiii.Ml l)y ill.- f^nidiciil, v..liiin.-, .■mil l<.;i.l. Wltcii ;i sln-am is nv..rl.)a<h-<l 
Willi s.-(liiiiciil, llic excess is .lioppcd. When it is uiKleilo.ided, it erodes. When 
eiinililiriiiiii li.is lieen esl.ihlished, neilher eiosiun nor deposition t.ikes place. Cr.idient, 
voliiine, .Old load usually vary in the s.iine stre.ini so th.it d<-position may he k'<'inK 
on in one i).irt of its valley .ind erosion in .•mother. Wiien a stream is erodin;,', the 
material within reach of its .-ictivity is constnntly moved in a downstream direction. 
All m<ivements of (his kind are .-iccomplished hy more or less sortin;; and make for 
the concentr.it ion of the heavier i)articles. 

"Deposition takes place in .a stie.im when the velocity is decre:ised, either liy 
the periodic chaii},'es in volume or hy a ch.iime of ;;radieiit. Whore there is a chanu'c 
of K'rade, resulting in diminished velocity, the ^'old is laid down with the other sedi- 
ments. -It must he rememhered, however, that placer .i;old may find lodgement in 
inequalities of the Ix-drock surface where no coiisidenihle deixisition of detrilal m.atter 
has taken pl.-ice, thoufih extensive placers are, as a rule, not formed hecause of 
irre>;ularities in the hed-rock surface ahine. The concent r:it ion of -old in river hars 
is analoj;ous to its deposition in stream he<ls. for it is dropped where the velocity of 

the current is oheckod hy the form.-ition t>f eddies, due to the i pialities of the river 

floor." 

A further study of this subject is uuide herein in coiiiieetiun witli 
the more detailed analysi.s of stream action. 

When tlie bed of a stream is the actual rock floor of the valley, 
it is called 'bedrock' in the true sense of the word. Later in its history 
tile stream may flow on an aggraded bed of gravel or other sediment. 
If the stream gravels become covered with volcanic or other materials, 
the stream is obliged to flow over this new cover, called 'false-bedrock.' 
Gold particles are normally deposited on or near the bed of the stream, 
which Is called 'bedrock' or 'false-bedrock' according to whether the 
bed is the true hard rock floor of the valley or whether it is a super- 
ficial layer of clay, volcanic tuff, or some such imjiervioius material 
overlying previotisly deposited gravel. It is readily surmised, .there- 
fore, that tliere may be two oi- more tiers of gold-bearing stream channels, 
but the ui)per ones do iiot necessarily lie directly above the older and 
lower chamiels, and may not follow the direction of their courses at all. 
If the .stream cuts clear down to the true bedrock, remnants of the older 
channels will lie at relatively higher positions instead of at lower hori- 
zons. In some cases, where gravel is deposited deeply on bedrock, 
forming a new aggraded bed, rejuvenation of the stream will .stir uj) the 
entire mass of gravels, including the gold-bearing layer deposited on 
top, and the final residt will be that most of the gold particles will reach 
a position very near true bedrock. The complexity of the history of 
thesQ processes is apparent; so also are the difficidties of the engineer 
who attempts to do a fair job of sampling. 

"> Brooks, Alfred H., op. cit., p. 12S. 



See. II] GEOLOGY OF PLACER DEPOSITS — .JENKINS 179 

In excavating for the Boulder Dam a sawed plank of lumber was 
found 60 feet deep, ' ' lying under gravel on the edge of the inner gorge, 
a place that it could not have reached in any imaginable way except by 
burial during some comparatively recent flood." °" This case and many 
others show that the depth of burial by recent rivers does not necessarily 
mean that a great period of time has elapsed for the accumulation of the 
deposit. During high water, the whole ma.ss may be stirred up and even 
boulders floated in the soupy mixture of heavy rock debris and water. 
This action gives the gold particles a chance to work their way toward 
the bottom of the mass. 

For thousands of years particles of gold of various sizes, from nug- 
gets to Hour gold, were dropped and lodged in the riffles of bedrock along 
the natural river-sluices of the Sierra Nevada. Flattened particles are 
most- easily carried; sometimes, suspended by air-films, tiny scales even 
float on the surface of the water."' Extremely fine grains of gold were 
swept by torrents through the canyons and out into the Great Valley. 
In the present dredging grounds where they are found, they have been 
easily caught in false-bedrock, which consists of clayey layers of volcanic 
tuff.' 

The very high specific gravity of gold, six or seven times that of 
quartz, with the ratio increasing to nine times under water, is the primary 
factor which causes this heavy resistant metal eventually to work its way 
to a point where it may sink no farther. Once it is caught on bedrock, 
the stream has great dif!iculty in picking it up again. 

When a stream leaves its mountain canyon and enters a more level 
country or a still body of water,, the materials carried by that stream are 
deposited in the form of a fan or delta. At the apex of this fan or delta 
fine gold may be deposited, and ma^' never reach bedrock. It may be 
deposited on top of clayey, 'false bedrock' layers. The stirring action 
found to occur in rugged mountainous canyons during time of floods, 
which permits gold to reach bedrock, does not take place in the delta. 

Lindgren state : '''' 

"Bj- an odd paradox, gold is at the same time the easiest and most diflicult mineral 
to recover. It is divisible to a high degree and owing to its insolubility the finest par- 
ticles are preserved. A piece of gold worth one cent is without trouble divisible into 
20<K) parts, and one of these minute particles can readily be recognize<l in a pan." 

Although gold is verj'^ malleable, and may be hammered into differ-* 
ent shapes by stones hitting it as they tumble along in the stream, dif- 
ferent particles are not Avelded together to form larger nuggets, as some 
people are prone to believe. Lindgren" has sho\m that the largest 
masses of gold have come from lodes, not placers. Particles of gold may 
be broken down, however, from another piece. The more rounded or 
flattened nuggets have probably gone through more knocking about than 
the rougher pieces. Those showing the original crystalline forms have 
probabl}' not traveled far in the ' free ' state. 

It is also found that the more ancient placers, and those which have 
undergone many reconcentrations, contain gold of a higher degree of 
fineness than those whose source is near by, or in which the gold has not 

" Berkey, Charles P., Gorge excavation confirms geological assumptions : Eng. 
News-Rec, vol. Ill, p. 762, fig. 2, 1933. 

" Lindgren, W., Mineral deposits, p. 220, 1919. 
62 Lingren, W., Mineral deposits, p. 220, 1919. 
" Lindgren, W., op. cit., Tertiary gravels, p. 66. 



180 



PLACER mining; FOR COLD LV CALnX)RNIA 



[Bull. 135 



^ ^laUlckl 





"^ 


r=r 




;!i^ 












- 




a 


b 


c 


cf 


- 


^ 










- 












::;^ 








1 



Fig. (iS. Diagram to represent the theoretical 
effect of incroa.scd velocity (V) on transporting power 
(Toe) of a stream; uftcr ChumhcrXaxn and HdlisbiDii. 
TocV", i.e., if the velocity i.s douhled, the transiiorting 
power increases as much as (i4 times. 

"A statement more frequently encountered is to 
the effect that the qyantity varies with the sixth power 
of the velocity ; and the origin of thi.s assertion is now 
in douht. It is an erroneous version of a deductive law. 
. . . The law, as formulated l)y Hopkins, is that 'the 
moving force of a current, estimated l)y the volume or 
weight of the masses of any proposed form which it is 
capable of moving, varies as the sixth power of the 
velocity' ; and this law pertains not at all to the (|uantity 
of material moved, but to the maximum size of the 
grain or pehhle or boulder a given current is competent 
to move." Gilbert, G. K., The transportation of debris 
by running water: U. S. Geol. Survey Prof. Paper 86, 
pp. 15-16, iyi.i. 



Sec. II] GEOLOGY OF PLACER DEPOSITS JENKINS 181 

been deposited for sueli a long period of time. This may be due to the 
removal of alloyed silver by the dissolvinj; action of surface waters." 

The solution and reprecipitation of gold in the gravels is shown 
to be exceedingly rare or nonexistent, commercially.'*-^ On the other 
liand, in some of the Tertiary channels, thin crusts of pyrite or marcasite 
are found deposited on the surface of the gold particles themselves. 

Factors of Concentration 

A placer worthy of mining is like any other commercial mineral 
deposit in that it is a special case of concentration due to several com- 
bining natural processes which were all in favor of the accumulation of 
the one desired mineral. Source, release, transportation, deposition, 
reconcentration, and retention of the gold have already been discussed. 
Three extremely important factors are: (1) Structural control of the 
stream pattern, so that the streams run along the course of the zones 
of mineralization; (2) Decay and disintegration at the surface of the 
mineralized rocks prior to erosion ; (3) A change in the cycle of erosion, 
causing rejuvenated flow of streams and the rapid washing of the 
released gold into stream channels. 

Quoting from a recent paper appearing in the Engineering and 
Mining Journal :^^ 

"Accumulation of gold in an important placer deposit is rarely a mere coinci- 
dence ; it is rather the fortuitious concurrence of several favorable factors. In regions 
where nature has bestowed the advantages of extensive mineralization, rapid rock 
decay; and well-developed stream patterns, a relatively large amount of gold placer 
may be formed. But even in this ideal case, the favorableness of these several 
important factors must be assumed. 

"The general considerations which favor the accumulation of gold in special 
locations have been frequently discussed. Physically, the phenomenon is simple ; in 
such locations where the gold has been deposited, the transporting power of the 
stream has become insufficient to carry away the particles of gold that have settled. 
The richness of the deposit will therefore depend not only upon the completeness of 
this loss of transporting power, and on the ability of the bedrock to hold the deposited 
gold at this point, but also, most importantly, on the general relationship of the gold 
sources to the stream. The early miners untiringly sought the 'ledge' or 'raothor 
lode' which furnished certain rich placers. However, with the presence of mineralized 
zones as a source of the gold, the richness of a placer is perhaps due more to the 
efficiency of the stream as a concentrating device than to its uncovering rich lode 
deposits. 

"The ability of a stream to transport materials is essentially dependent upon 
the velocity of the water and the area and specific gravity of the particles of material 
being carried. The transporting power of water varies approximately as the sixth 
power of the velocity. This means that even small velocity changes have an 
enormous effect upon transporting power, ranging rather abruptly from velocities 
which can not transport an appreciable amount of gold to those which easily trans- 
port much of the gold that may enter the stream or be released from the gravels 
therein. The velocity of water is a complex relationship of grade, shape, and size 
of the channel, quantity of water, and other factors. A grade ranging from 30 to 
approximately 100 ft. per mile will favor the deposition of gold. With appropriate 
conditions of flow, these limits may be somewhat increased or reduced without serious 
handicap. When considering the grades of the ancient channels, however, one must 
remember that faulting and regional tilt often have considerably modified the original 
grade. 

"For the richest accumulations, the erosional conditions must be well balanced, 
so as to provide a long period of concentration. Slight uplifts tend to rework and 
further enrich placer deposits, as do increased volumes of water, inasmuch as both 
of these factors tend to increase the velocity. Local variations in the shape of the 

^* Lindgren, W., opf'cit., Tertiary gravels, p. 68. 
" Lindgren, W., op. cit., Tertiary gravels, p. 69. 

5« Jenkins, O. P., and Wright, \V. Q., California's gold-bearing Tertiary channels: 
Eng. and Min. Jour., vol. 135, pp. 501, 502, November 1934. 



182 



I'LACKU .MININC FOR (iOIJ) IX CAI.irOKNIA [null. V\7) 




Fig. 69. Ideal vertical section of a delta, show- 
ing in greater detail than figure "0 the typical succes- 
sion of strata : A, topset ; B, foreset ; and C, br)ttomset 
beds. After Gilbert, U. S. Gcol. Survey 5th Ann. Rent. 
188S. 



y>xi^ 









ro. Ideal cross-section of a delta showing A, topset ; fi. foresot ; and C. liottom- 
set beds. After Gilbert, U. S. Geol. Survey 5th Ann. Rept., 18H3. 



Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 183 

channel are of most interest, however, because they are immediately responsible for 
specific deposits of placer gold. When a stream canyon widens out, deepens, turns, 
or joins another watercourse, certain zones of concentration will be formed where 
(he water velocities have been somewhat reduced and where eddy currents occur. 
These reductions in velocity immediately allow >;old and heavy mineral particles to 
separate from the mass of gravel that is beinjr carried and rolled down the canyon. 
Gold has a specific gravity of approximately .six times that of the gravel, but under 
water this ratio becomes about nine times. This large gravity difference permits 
the gold quickly to work its way to bedrock and into any crevices therein. Here 
it remains, requiring excessive erosion to remove it to new locations. 

"In order that a major deposition of gold may occur, there must be an abundance 
of source material which contains more or less gold and which may be more or le.ss 
easily eroded. A decayed formation of low-grade material could easily furnish more 
gold than a hard, higher-grade deposit. The decomposed material also supplies more 
gravel for balanced conditions of stream transportation, providing that overloading or 
choking is minimized by uplifts or increasing water volumes. Plainly, a stream 
running along a vein system will have a greater opportunity to accumulate gold than 
one merely crossing it. Bedrock-controlled streams, therefore, provide a maximum 
contact with source material. 

"A further and very important factor is the ability of bedrock to hold the 
deposited gold in spite of the .scouring action of the stream at higher water stages. 
A smooth, hard bedrock is a very poor one for placer accumulations. Bedrock 
formations which are decomposed or possess cracks and crevices are good, and thos(^ 
of a clayey or of a schisto.se nature are excellent in their ability to retain particles 
of gold. 

"Gold tends to resist most stream transportation. Coarser gold will migrate 
downstream an amazingly short distance from its apparent source throughout a 
long erosion period. The fine gold, which the stream can transport, is dropped rather 
completely within a restricted area at the mouth of the stream canyon." 

Age of Placers 
Significance 

The geologic age of a placer deposit is often a factor of primary 
economic interest. In the Sierra Nevada, the oldest system of Tertiary 
channels has proved to be the richest, for it was formed prior to the 
extensive volcanic activity which resulted in the covering of the min- 
eralized bedrock surfaces as well as the valleys in which gold-bearing 
streams flowed. These streams, which cut directly through the mineral- 
ized zones, had an ideal opportunity to tap the primary gold resources 
of the region, while those which flowed only over a barren volcanic 
cover remained themselves barren of gold. In the region of the buried 
channels of the Sierra Nevada, many stream deposits of different 
jjeriods are now found intermingled. To decipher their history and 
relative age is an essential part of the exploration geologist's work, in 
his search for the channels of greatest possible economic consequence. 

Structural Criteria 

Various criteria are used in determining the relative age of stream 
deposits, but the most positive evidence is structural relationship. 
For example, the cutting chaiuiel is younger than the channel which 
it cuts. 

The deepest channel is not necessarily the oldest nor yet the 
youngest. In the case of the modern canyons of the Sierra — the 
youngest are the deepest ; yet along the western foot of the range the 
present streams floAv over older channels buried beneath. "Where a 
canyon is filled with detritus or with lava, the newer stream flows on 
top of the deposit and is therefore higher than the old stream-bed 
beneath, while still more ancient stream terraces or benches may lie 
at higher and varving elevations on either side of the canvon. Some 



184 PLACER JIIXIXG P'OR GOLD IN CALIFORNIA [Bull. 135 

benches, representiii}; former streams, may liave even been left prior 
to a lava tlow eoverin<; the deepest clinnnol, while other benches may 
have been left later. 

It is a]iparent. therefore, that the subjects of historical sequence 
jind relative a^'^e are matters of detailed jreolojric and physio^M-aphie 
study which deserve more than superficial examination. They cainiot 
be classified by do}rmatic rules. 

Paleontologic Criteria 

In order to assijin definite jreolojric periods to the deposits of 
ancient streams, their ajre should be related in some way to the well- 
established epochs of rejiional jreolojric history. Fossils, dia«rnostic in 
determination of p-eolojiic periods, if found in the stream deposits, are 
of inestimable value in this rep:ard. 

In the Sierra Nevada, parts of fossil plants consistinjr of leaves, 
lo<rs. etc., have been extensively collected and determined by paleo- 
botanists. Also, some vertebrate bones have been sent from the old 
drift mines to the Smithsonian Institution and elsewhere for scientific 
study. 

fJeolojric periods the Avorld over have been established larp:ely on 
their marine fauna rather than their continental fiora or fauna. For 
instance, marine beds of the Tone formation contain fossil sea-shells 
definitely assijrned by iialeontolo<rists to the Eocene, or earliest Tertiary 
l)eriod. Tiie fossils found in the sediments filling- the Tertiary valleys 
of the Sierra are iiot, however, marine, but are of ancient lands and 
lakes. Correlation of jieoloiTric ajze by means of these land plants and 
land animals brings in complications that have not yet permitted the 
two bases of criteria, marine and nonmarine, to be perfectly coordi- 
nated. Besides, most of the fossil leaves occur in tuffaceous lake beds 
that overlie the frold-bearinjr quartz-jri'avel deposits, aiul therefore do 
not yive much direct evidence as to tlie a<re of the latter. Fossil wood. 
so common in the most ancient of the <::old-bearin«r u ravels is not as 
yet determinable nor diaji-nostic. In most cases it represents unstudied 
tropical forms which have been placed in the Eocene by paleobotanists 
because of the known climate of that period. The older jrravel con- 
tainin<r this fossil wood has i)reviously been referred to the Cretaceous. 
In the Smartsville (|uadran<rle, for example, a deposit containin<r pet- 
rified lofrs of probable Eocene ajre is described by Lind<iren as follows:'' 

'•Tli»' hiKli. is()liit«Ml jirca of \v«'ll-\viisliM(l Krnvpl .S miles north-iK.rthwfst of 
Montezuma Hill is Ilote\vr»^tll.^ ; it is so much liiuher than the adjiu-eiit uravel channel 
of North San .Tn.in that it must be assumed to Itelonn to an e.irlier period ; very 
likely it is of Cretaceous age." 

It is a fact, however, that no fossils indicatinp- a Cretaceous ajre 
have yet been found in these older jrravels. Wherever definite marine 
Cretaceous beds do occur on the western foot of the Sierra Nevada the 
oldest stream channels of the vicinity are foui^d to cut the Mesozoic 
.sediments, showinjr a profound difference in ajre between the two. 

Chaney •"'•'* sunnnarizes the results of i)aleobotanical study of the 
fossil plants found in the Sierra Nevada as follows: 

••• LiiKlnren. W., op- <it., TiTtiary uravvls, p. 12^. 

■'""Chaney, Ralph \V., Notes on occurrence and age of fo.s.sil plant.'< found in the 
auriferous travels of Sierra Nevada : California Div. Mines, Mining in California, State 
Mineralogists Rept. 28, p. 301, 1932. 



Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 185 

"The tiiflfs and shales in which fossil plants occur interbedded in the Auriferous 
Gravels range in age from lowermost Kooene to upper Miocene. During this time, 
there was a climatic trend from suhtroiiical to temperate conditions, which resulted 
in the elimination of palms :iud other large-leafed species .Mnd the incoming of types 
of jdants similar, in general, to those now living in Xorth America. The Miocene 
flora indicating ;i temperate climate, includes genera no longer living in western 
America, although they occur in e;istern America and eastern Asia. 'JMie evidences 
of <lifference in living conditions in the Koceiie and t]i(> .Miocene make it possible 
readily to dilTerentiiile iietween the older and the younger floras of the Auriferous 
Gravels." 

Mo.st of the fos.sil vertebrate bones de.scribed from the drift mines 
of the Sierra Nevada have been collected and sent in to paleontologists 
by persons who did not record their definite location, so that the exact 
geologic formations in which the fossils were embedded are unknown. 

The paleontologist who works with vertebrate remains is not always 
apt to apply the same age to beds as that which has been assigned them 
by the paleobotanist ; generally the former assigns a younger age. ^lany 
of the well-established Sierran Tertiary as well as later beds containing 
vertebrate bones were once given the blanket designation of Pleistocene.''^ 

Physiographic Criteria 

Age correlation has sometimes been done purely on physiographic 
evidence. Matthes ^^ assigns Eocene, Miocene, Pliocene, and Quater- 
nary periods of uplifts to the various old surfaces found in the 
Yosemite region, tying in the Miocene surface correlation with geologic 
features of a fossil leaf locality occurring in the Tuolumne Table 
Mountain region. The fact that old surfaces have been resurrected ^^ 
during the Pleistocene has only recently been given consideration. 

"Quaternary erosion resulting in the uncovering of Tertiary volcanic ash and 
the resurrection of early Tertiary surfaces, formerly cut into pre-Cretaceous bedrock 
along the western flank of the Sierra Nevada, is a widesjjread geologic process which 
has heretofore not received the recognition it deserves. The process inv<dves features 
of vast economic concern. One key locality for this study is in the region of Table 
Mountain, Tuolumne and Calaveras counties, California, where a very resistant late 
Tertiary latite flow has served the purpose of preserving not only fragments of 
earlier and less resistant geologic bodies consisting of volcanic materials, mud flows, 
lake beds, and stream gravels of different ages, but also the underlying bedrock 
surfaces of earlier Tertiary age. These ancient surfaces, the topography of which 
appears to have been controlled by bedrock structure, may be (ound in various stages 
of resurrection. In this are.a, the gold-bearing gravels were mined in ancient chan- 
nels that ran in directions opposite or at an angle to the Table Mountain Channel ; 
the latter apparently never contained any appreciable amount of gold-bearing gravel, 
contrary to the common belief. Though unmantled and dissected through Pleisto- 
cene and Recent epochs, fragments of upland peneplained bedrock aiul in places 
gravel-covered surfaces are actually early Tertiary land forms, which have been 
brought to light after having been buried throughout later Tertiary volcanic epochs." 

Lithologic Criteria 

The nature and composition of the material filling the ancient 
channels and valleys also indicate to what geologic period a deposit 
may belong. Gold-bearing gravels, composed purely of sand and 
quartz-pebbles, or of the bedrock complex, indicate that the channel 

=" Hay, Oliver P., The Pleistocene of the western region of Xorth America and it3 
vertebrate animals : Carnegie Inst. Wash., I'ub. 322-B, 1927. 

"" Matthes, Francois E., Geologic historv of the Yosemite Valley : U. S. Cenl. Sur- 
vey, Prof. Paper 160, 1930. 

"1 Jenkins, Olaf P., Resurrection of eaiiy sui-faces in the Sierra Nt- vada : California 
Jour. Mines and Geology, vol. 30, p. 5, 1934. 



186 



PLACER MINING FOR GOLD IN CALIFORNIA 



[Bull. 135 



is of the pre-volcanic period, possibly Eocene in age. Mo.st of the 
rhyolites were apparently formed during the latter part of this period 
and in the Oligoeene. The most abundant of the volcanic rocks are 
composed of andesites, which seem to be largely of late Miocene or 
early Pliocene age. During the late Pliocene and early Pleistocene 
there were many basalt flows. Tuolumne Table Mountain is composed 
of latite. probably of late Pliocene age. 

In the Recent period much pumice has been expelled from craters 
and blown over various parts of the Sierra Nevada. 

Streams may always be considered younger than the rocks from 
which tlieir gravel has been derived, though mud-flows may receive 
their materials from active volcanoes. There is here an opportunity 
for a petrographic study of both volcanic rocks and the materials of 
the sediments. Special detailed analysis of stream correlation might 
be performed by means of the method known as "heavy mineral separa- 
tion," previously mentioned as widely employed in petroleum geology. 

Coordination of Criteria 

In order to assign a geologic age to a placer, all criteria should be 
sought out and used so far as it is possible. A regional study of age 
relationship should include a coordinated study of all phases: struc- 
ture, fo.ssils, surface features, and materials deposited. 

The principal placers in California occur in the Quaternary, 
Tertiary, and Cretaceous geologic time divisions, which are grouped 
in the following manner : 



Eba 



Cenozoic 



Period 
Quaternary 



Tertiary 



Epoch 
Recent 



Pleistocene 



Duration 

in millions 

of years 



(Neocene 1 Pliocene 

or 
Xeogene) J Miocene 



IniiKocene 
Eocene _. 



I Cretaceous 75 
Jurassic 40 
Triassic 40 

Paleozoic 415 

Proterozoic Unknown 



Life History and Habit of Streams 
Need for Scientific Background 

p]xploration of placers and various ancient stream channels requires 
an understanding of the habits and life history of streams in general 
This includes, on the one hand, processes of erosion and deposition 
and on the other, physiographic history. Each is iinportant; the first 
more directly, while the second has to do with regional features, knowl 
edge of which is essential to the exploration geologist. The funda 



Sec. II] OKOLOGY OF PLACKR DEPOSITS JENKINS 187 

mental science of streams has been outlined in a simple yet splendid 
manner by G. K. Gilbert"- in his masterpiece on the Henry Mountains, 
Utah. Later, I. C. Uussell published an excellent text on streams.®^ 

Such natural processes as those related to streams are so universal 
that a study of them in one part of the world may be applied to con- 
ditions found in another. Similarly, an understanding? of the ancient 
Tertiary streams of the Sierra may be jjained by applying the knowl- 
edjre of processes found in operation today where conditions and envi- 
ronments would appear similar. 

In a province, such as the Sierra Nevada, where the development 
of the drainajre system has been repeatedly interrupted by earth move- 
ments or by burial as a result of volcanic mud washes and lava flows, 
the history of the stream of any one chronological horizon is a separate 
entity, and may be entirely different in form and pattern from either 
earlier or subsequent systems. This fact, together with the complexity 
of any one system presents a problem much involved. 

The need for a scientific background in the study of streams is 
therefore apparent. The more pertinent features of this study, together 
with its terminology, are outlined in the following pages. 

Stream Erosion 

Stream or fluvial erosion is complex. It may be divided into the 
several processes: hydraulic action, abrasion, solution, and transporta- 
tion. A brief statement of the essential factors which control erosion 
is quoted from an authoritative textbook^'* as follows : 

"The capacity of a stream to erode depends on its volume and velocity. The 
velocity in turn depends on (1) the slope down which the stream is flowing, (2) volume 
of water, (3) the shape of its channels, and (4) weight and volume of its load. 

"The rate of descent nf the bed of a stream is the stream gradient. It is 
ordinarily expressed as so many feet per mile. The gradient changes from place to 
place along the course of the stream. Velocity increases rapidly with increase of 
gradient. Thus mountain streams with high gradients erode their valleys much more 
quickly than lowland streams of comparable size with low gradients. It follows that 
streams wear high gradients down to low ones by continued erosion, and that as the 
gradients are worn down the rate of erosion must decrease. 

'"The volume of water is a variable factor in all streams, largely because of 
fluctuations in rainfall. Velocity and rate of erosion in any stream are therefore 
always changing. As a rule, these changes are too slight to be readily noticeable, 
but in some regions they are great enough to cause streams to dry up at certain 
seasons, and to rise in floods at others. In other regions fluctuations are less extreme. 
Every spring the lower Mississippi has a normal rise in water level of 15 to 20 feet. 
The Nile normally rises 24 feet and the Ganges 32 feet. The erosive effect of such 
floods is considered below. 

"The shape of the stream channel as seen in cross-section also influences velocity. 
Since friction between water and channel slows a stream down, velocity is greatest 
in channels with the smallest area in proportion to volume of water. Deep, narrow 
channels therefore give -greater stream velocity than broad, shallow ones. 

"A stream continues to acriuire a load until it is carrying the greatest possible 
amount permitted by the gradient, volume of water, and kind of material available." 

The "laws of erosive power" concern both transportation and 
abrasive power of the stream. If all the fragments of rocks had the same 
specific gravity, then the folloAving definite action would take place. 



'« Gilbert, G. K., Report on the geolog> of the Henry Mountains : U. S. Geog. and 
Geol. Survey of the Rocky Mountain Region, Chap. V, Land Sculpture, pp. 9 9-150, 1877. 

'*' Russell, Israel C, Rivers of North America, a reading lesson for students of 
geographv and geology, <;. V. Putnam's Sons, 1S98. 

8* Longwell, C. R., Knopf, A., and Flint, R. F., A textbook of geology, pt. 1, physical 
geologv, pp. 42-44, ^ohn Wiley & Son.s, 1932. 



188 PLACER MIXING FOR GOLD IN CALIFORNIA [Bull. 135 

"If the volocity of a stream l>c doubled, tlie diameters of rock fratjments it can 
move are increased 4 times. In other words, the majimuin lUnmcler of the individwil 
rock frngments a stremn cnn move varies ns the siiunre of the retocity. • * * 
Calculations have shown that douhluig the velocity of a stream increases its abrasive 
power at least 4 times, and under certain conditions as much as 04 times. In oth^-r 
words, nhranive power varies hetueen the sijunre and the sij-th pouer of the velociti/. 

"These laws not only explain the vastly jjreater erosion accomplished by swift 
streams than by slow ones under normal cttnditions, but they show clearly why 
exceptional Hoofis, greatly increasing velocity by increasing volume, have such tremen- 
dous destructive power. The volume of the Colorado Uiver measured at Yuma, 
Arizona, during a fiood in 1021, was l."» times its normal volume. Again, when the 
St. Francis Kam near J-os Angeles gave way in 1!»2S :ind Hooded the valley below, 
huge blocks of concrete weighing up to 10,t)(K) tons each, were moved by the escaping 
water. In India, during the (;ohiia Hood of ISl)."), which lasted just four hours, the 
water picked up and transported such quantities of gravel that through the first V.i 
miles of its course the stream made a continuous gravel deposit from 50 to 234 feet." 

Preparation of Material Removed by Erosion 

As previou.sly stated and described, tlie materials which are removed 
and washed into the streams are first prepared through weathering 
processes. Particles are loosened from the outcrop by surface disintegra- 
tion, consisting largely of oxidation, h^'dration, and solution. 

Since climatic environments were different in the past than they 
are now, the subject of ancient climates''^ is an important problem in 
its relation to the development of ancient stream channels. The study 
of fossils imbedded in the deposits gives the most important clue to the 
nature of ancient climates. The condition and composition of the sedi- 
ments themselves give another, as repeatedly pointed out by Reed.^*^ 

Transportation 

Tlie subject of river engineering brought forth at an early date much 
definite information as regards the carrying power of streams. The 
following statement is quoted from Stevenson :^' 

"The following are results deducted from experiments made by Bossut, Dubuat, 
and others, on the size of detrital particles which streams flowing with different 
velocities are sai<l to be capable of carrying: 

.'{ in. per sec. — 0.170 mile per hour, will just begin to work on fine clay. 
(J in. per sec. — 0.340 mile per hour, will lift fine sand. 
S in. per sec. — 0.4545 mile per hour, will lift sand as coarse as linseed. 
10 in. per sec. — 0.5 mile per hour, will lift gravel the .size of peas. 
12 in. per sec. — O.OSID mile per hour, will sweep along gravel the size of beans. 
24 in. per sec. — 1.30.38 miles per hour, will roll along rounded pebbles 1 inch in 
diameter. 
3 ft. per sec. — 2.045 miles per hour, will sweep along slippery angular, stones 
the size of a hen's egg." 

The following table is quoted from F. C. Gilbert*^^ to show the 
maximum diameters of boulders which can be moved in sluices at certain 
velocities: 



"'■Smith, J. p., Ancient climates of the West Coast: Pop. Sci. Monthly, vol. 76, pp. 
478-486,1910. . . . Climatic relations of the Tertiary and Quaternary faunas of the 
California region : California Acad. Sci., Proc, ser. 4, vol. 9. pp. 123-173, 1919. 

"" Reed, Ralph D., r.eology of California, Am. Assoc. Petroleum Geologists, 1933. 

" Stevenson, Oavid, The principles and practice of canal and river engineering, 
p. 361, lOdinburgh, 1886. 

»* (Gilbert, F. C, Design of sluices for gold placer mining : Eng. Jour., Arizona, vol. 
16.no. 8. p. 4, 1932. 



Sec. II] OEOLOOY OF PLACKR DEPOSITS — JENKINS 180 

Diameter ^ olocity 

(inches) (f''*'t P<'i- s<'<-'>n<l) 

o __ _ _ a.a 

4 ::::::::: ri.^ 

6 G.2 

8 7.4 

10 : 8.4 

lo 0.1 

1(5 lO.S 

20 11.0 

24 i:^o 

30 y-''"* 

Trausportalioii, as sliuwii by Medoe,'"' is done by tlie carryiii<; of 
materials in solution, through suspension, and by tiie process of saltation. 
The materials thus carried are deposited by precipitation from solution, 
sedimentation from suspension, and grounding after 'leaping' along by 
that process called 'saltation.' 

It lias been shown by (1. K. Gilbert,'" who carried on extensive 
laboratory experiments with running water, that the materials borne in 
suspension are easily enough sampled and tlieir quantity measured ; but 
the 'bed load' is much less accessible. This load is carried forward by 
sliding or rolling along a smooth channel bed, as well as by saltation, 
which takes place when the bed is uneven and causes the particle to move 
irregularly in a series of jumps. 

Gilbert calls the transportation of the bed load "hydraulic traction" 
in contrast to "hydraulic suspension." His summary of "Modes of 
transportation, collective movement" is expressed as follows: 

"When the conditions are such that the bed load is small, the bed is molded 
into hills, called dunes, which travel downstream. Their mode of advance is like 
that of eolian dunes, the current eroding their upstream faces and depositing the 
eroded material on the downstream faces. With any progressive change of condi- 
tions tending to increase the load, the dunes eventually disappear and the del)ris 
surface becomes smooth. The smooth phase is in turn succeeded by n second rhythmic 
phase, in which a system of hills travel upstream. These are called antidunes, and 
their^movement is accomplished by erosion on the downstream face. Both rhythms 
of debris movement are initiated by rhythms of water movement." 

In showing how complicated a stream 's action may be, Gilbert states : 

"The flow of a stream is a complex process, involving interactions which have 
thus far baflBed mechanical analysis. Stream traction is not only a function of stream 
flow but itself adds a complication. Some realization of the complexity may be 
achieved by considering briefly certain of the conditions which modify the capacity 
of a stream to transport debris along its bed. Width is a factor ; a broad channel 
carries more than a narrow one. Velocity is a factor ; the quantity of debris carried 
varies greatly for small changes in the velocity along the bed. Bed velocity is 
affected by slope and also by depth, increasing with each factor; and depth is 
affected by discharge and also by slope. If there is diversity of velocity from place 
to place over the bed, more debris is carried than if the average velocity everywliere 
prevails, and the greater the diversity the greater the carrying power of the stream. 
Size of transported particles is a factor, a greater weight of fine debris being carried 
than of coarse. The density of debris is a factor, a low specific gravity being favor- 
able. The shapes of particles affect traction, but the nature of this influence is not 
well understood. An important factor is found in form of channel, efficiency being 
affected by turns and curvature and also by the relation of depth to width. The 
friction between current and banks is a factor and therefore likewise the nature of 
the banks. So, too, is the viscosity of the water, a property varying with temperature 
and also with impurities, whether dissolved or suspended." 

60 McGee, W. J., Outline of hydrology : Geol. Soc. America Bull. 19, p. 199, 1908. 
"" Gilbert, G. K., The transportation of dfibris by running water : U.S. Geol. Survey 
Prof. Paper 86, pp. 10, 11, 15, 16, 1914. 



190 PLACER MINING FOR GOLD IX CALIFORNIA [Bull. 133 

Gilbert classifies streams according to their transportational char- 
acters : 

"The classification of streams here Riven has no other purpose than to afford a 
terminology convenient to the sul)ject of (K'bris transportation. 

"Wiien the (l<'bris supplied to a stream is less than its capacity the stream 
erodes its bed, and if the condition is other than temporary the current reaches 
bedrock. The dragging of the load over the rock wears, or aiirades, or corrades it. 
When the supply of d^'bris equals or exceeds the capacity of the str«'am bedrock 
is not reached by the current, but the stream bed is constituted wholly of debris. 
Some streams with beds of debris have channel walls of rock, which rigidly limit 
their width and otherwise restrain their development. Most streams with beds of 
debris have one or both banks of previously deposited debris or alluvium, and these 
streams are able to shift courses by eroding their banks. The .several conditions 
thus outlined will be indicated by speaking of streams as conadhifi, or lock-icnlled, 
or alluvial. In strictness, these terms apply to local pha.ses of stream habit rather 
than to entire streams. Most rivers and many creeks- are corrading streams in parts 
of their courses and alluvial in other parts. 

"Whenever and wherever a stream's capacity is overta.\ed by the supply of 
debris brought from points above a deposit is made, building up the bed. If the 
supply is less than the capacity, and if the bed is of d^^bris, erosion residts. Through 
these processes streams adjust their profiles to their supplies of debris. The i)rocess 
of adjustment is called gradation ; a stream which builds up its bed is said to aggrade 
and one which reduces it is said to degrade. 

"An alluvial stream is usually an aggrading stream also; and when that is 
the case it is bordered by an alluvial plain called a flood plain, over which the water 
spreads in time of flood. 

"If the general slope descended by an alluvial stream is relatively steep, its 
course is relatively direct and the bends to right and left are of small angular amount. 
If the general slope is relatively gentle, the stream winds in an intricate manner; 
part of its course may be in directions opposite to the general cour.se, and some of 
its curves may swing through 1S0° or more. This distinction is embodied in the 
terms direct alluvial stream and meandering stream. The particular magnitude of 
general slope by which the two classes are separated is greater for small streams than 
for large. Because finene.ss is one of the conditions determining the general .slope 
of an alluvial plain, and becau.se the gentler sloi>es go with the finer alluvium, it 
is true in the main that meandering streams are associated with fine alluvium." 

Conmienting on the curvature of a channel, which greatly compli- 
cates the transportation and deposition of debris by a stream, Gilbert 
says : 

"In a straight channel the current is swifter near the middle than near the 
sides and is swifter above mid-depth than below. On arriving at a bend the whole 
stream resists change of course, but the resistance is more effective for the swifter 
parts of the stream than for the slower. The upper central part is deflected least 
and projects itself against the outer bank. In so doing it displaces the slow-flowing 
water previously near the i)ank, and that water descends obli(iuely. The descending 
water displacM's in turn the slow-flowing lower water, which is crowded towai;d the 
inner bank, while the water i»reviously near that bank moves toward the middle 
as an upper layer. . One general result is a twisting movement, the ui)per parts 
of the current tending toward the outer bank and the lower toward the inner." 
Another result is that the swiftest current is no longer medial, l)Ut is near the outer 
or concave bank. Connected with these two is a gradation of velocities across the 
bottom, the greater velocities being near the outer bank. The bed velocities near 
the outer bank are not oidy m\ich grt-ater than those near the inner bank, but they 
are greater than any bed velocities in a relatively straight part of the stream. They 
have therefore greater capacity for traction, and by increasing the tractional load 
they erode until an e(]uilibrium is attained. On the other hand, the currents which, 
cro-ssing the bed obliquely, approach the inner bend are slackening currents, and 
they deposit what they can no longer carry. 



T' The system of movements here described has been observed l)y many students of 
rivers. They were demonstrated by the aid of a model channel Ijy J. Thomson, in con- 
nection with an explanation which differs somewhat from that of the present text. See 
Roy. Sec. London Proc, pp. 5-8, 1876, and 35G-357, 1877; also Inst. Mech. Eng. Proc, 
pp. 456-460. 1879. 



S(H-. II] (iKOLOCY OK I'LACKK DKI'OSITS -.1 KN K INS 191 

"It rt'snlls tliiit tin- cntss scclinii on :i ciiivi' is :isviimit't ric, tlic ^'rc'itost dcplh 
Ix-iii- iH'iir tli<- niil.T l);mk. As IIm- windiiiu stn-.-ini cli.-iii^ios tlic direction of its 
ciirvnturf from oih" side to the oIIht. tiif twisliiiK system of current liliiments is 
reversed. :iiid with it tlie system of depth, Init tiie process of chiiUKe includes a jduisc 
with more tMiuuiile distrihut ion of velocities, und tiiis phase produces a slioal soparatinfj 
the two deeits. The shoal does not cross the cha!inel in a direction at rifjht angles 
to its sides liut is somewiiat ohli(pie in position, lending; to run from tiie inner bank 
of one curve to the inn<-r ItanU of the otiier. In meandering streams it is usually 
narrow and is .-ippropri.itely called a har. In direct alluvial str.-ams, where bends 
are apt to be separated by loiif;, nearly straif,'ht reaches, it is usually broad and 
may for ji distance occupy the entire width of thi« channel." 

Deposition 

The nature of slreaiu or fluvial (l('i)osits aiid t.lieir detailed structure 
and texture is described in various text')ooUs, but not with sufficient 
detail to explain all the types of complicated features found in f,'ravel 
deposits, especially complex deposits such as those of a mountainous 
region like the Sierra Nevada. 

Quoting- from Longwell, Knopf, and Flint '- on "fluvial deposition" : 
"The constructive process of fluvial deposition jcoes forward side by side with 
fluvial erosion. This is a result of the complexity and variability of the stream 
currents, which constantly drop some rock fragments to the bottom while they pick 
up others. When a stream is actively eroding its bed at a certain point, it is 
merely pickin;; up and carryinj; away more rock material than it is d<'positinf,' there, 
and when it is actively <lei)ositin>,' th** reverse is Koinj; on. Therefore, whereas 
fluvial erosion and deposition are processes iihysically o]>i)osed to each other, they 
can be separated in practice only by recognizinj; the preponderance of one over 
the other." 

The arrangement of materials deposited in a delta, however, is well 
known, and gives a picture which is more or less duplicated whenever 
the current of a stream is checked by a body of standing water and the 
materials transported are permitted to drop. The term 'foreset beds' is 
applied to the deposition on the frontal slope- of the growing embank- 
ment. ' Bottomset beds ' are of finer grain and are formed by the particles 
carried out beyond the slope and deposited in deeper water. 'Topset 
beds' are composed of the materials laid down and spread out on top 
of the other materials by the fluctuating stream. 

The material deposited by a stream is called alluvium and makes 
up fan, tloodplain, and delta deposits. The term 'fanglomerate' is used 
for the gravel materials of alluvial fans. 

An alluvial fan is built up at the point of abrupt change in 
gradient of a loaded stream. A floodplain is a series of coalescing 
alluvial flats along a valley. A delta is the final deposit by a stream, 
unloaded as it enters a still body of water. 

Overflow of a stream onto its floodplain will cause natural levees 
to be built up as low ridges bordering the channel. Lateral swinging 
of a stream causes cutting on the outer sides of the curves and depo- 
sition on the inside, w^hich results in the widening of the valley. A mean- 
dering stream may develop to the point of straightening itself in places 
by the cutting off and silting up of the meanders, forming oxbow lakes 
as a result. A stream w^hich forms a complex interlocking network on 
its floodplain typifies anastomotic drainage. An overloaded stream on 
a low gradient, becoming choked, and constantly obliged to cut new' 
channels, develops an intricate network on a floodplain ; the process is 
termed 'braiding.' 



Longwell, Knopf, and Flint, op. cit., p. 44. 



192 



I'LACKH MININC KOH COIJ) IN CALIFORNIA [Bull.135 



F=v ; tOj .. O. - T - H 1 l_ L S U O P E 




F O O 



H I "^L'-L' • S" l_"^50c->pr^j^E:-^^ 



F p O T - M ' •- ', L S L O 



■B"" d\T T^P~_M^=,'^^L'?^"1X>D3 



^ ® '_:-. 




Ji** S L O ■■ P E 



Fig. 71. A, Diagram to show a meandering .stream with oxbow loops. Such 
a stream develops in a valley worn down to ba.se-level and not subject to extensive 
floods B, Diagram to show a subdividing or anastomosing stream m a valley sub- 
ject to floods; (tfter Johnson, U. S. Ceol. Survey 22d Ann. Kept., 1^00. 



Sec. II] GEOLOGY OF PLACF.R DEPOSITS — JENKINS 193 

If the stream is rejuveiiated and therefore cuts deeper, floodplain 
terraces or benches are formed. The benches nia.y, however, be cut and 
left in the bedrock and covei-ed ^^ ith only a fihn of j:^ravel on the surface. 

Streams composed entirely of tiiick mud, called 'mudflows,' are 
akin to landslides.''' Quotinj? from Longwell, Knopf, and Flint : '^'^ 

"Aiiothor norin.'il tli<)H<;h iiifroqiu'iitly operative proco.'^.s in arid regions is 
the nnulflow. It occurs only where fine rock material becomes water-.soakecl on 
steep slopes after heavy rains, and moves downward as a slippery mass. ... It 
advances in waves, stopi)inj; when it hecoines too viscous to flow and damming the 
water behind it until it liquefies and again proceeds like an a<lvancing flow of lava. 
Mudflows can carry boulders many feet in diameter. Observers have seen these 
great rocks bobbing 'like corks in a surf.' Successive mudflows play a part in the 
building of fans." 

The transporting: power of mudflows, their various peculiarities, 
and the resultant un.sorted deposits have many characteristics much 
like those of glacial deposits and have frequently deceived engineers. 

The distingui-shing characters of glacial deposits are clearly sum- 
marized by Blackwelder, ' ■' who has made a special study of them : 

"The deposits left by glaciers should be distinguished from those made by 
streams, lakes and other agencies. 

"The ice tongue of a glacier leaves only one type of deposit called till. It is 
wholly unstratified and its components are quite unsorted — a jumbled orderless 
mass of clay, sand, and boulders. Blocks three to five feet in diameter are common 
and those 2.j feet or more are not rare. In general, the size of such boulders 
depends upon the spacing of the joint-cracks in the rocks of the mountain sides. 
Usually till is an earthy mass well si)rinkled with stones and boulders but in some 
cases the boulders predominate. This is particularly true of the deposits of small 
glaciers which have done little more than sweep the coarse talus from the valley 
slopes. The stones in till may be of any shape from well-rounded to angular but 
many have the corners and edges rounded. It is usual to find some that have been 
bevelled by being rasped along the bottom of the glacier. Hard rocks may thus 
be well polished. Such stones, like the bedrock, are covered with scratches which 
are easily recognized. 

"It is often difficult to identify till, especially if it has been much decayed or 
eroded or is poorly exposed. It may then be confused with other bouldery deposits 
which are unstratified. From volcanic mudflow deposits, .such as abound in the 
Miocene beds on the Sierra Nevada Hanks, till may often be distinguished by its 
containing large quantities of nonvolcanic rocks. Even this criterion fails where 
glaciers occupied volcanic mountains such as Mts. Shasta and Rainier. Ordinary 
mudflow deposits are seldom as thick as glacial moraines and are generally inter- 
bedded with typical stream gravel and sand, as in the alluvial fans of the arid 
regions. Unless the surface topography is still preserved or unless one finds plenty 
of scratched stones, it may be almost impo.ssible to distinguish till from landslide 
dumps. In many cases no one type of evidence can be relied on, but one must study 
all the facts and weigh the importance of each. 

"The rivers which issue from glaciers deposit coarse gravel, then fine gravel, 
and finally sand as the current weakens near the edge of the mountains. These 
three grades of detritus are more or less interbedded, because variations in the 
river's power occur from time to time at a given place. Like river deposits in 
general, those of glacial streams are distinctly stratified, though usually cross-bedded. 
They are fairly well .sorted into separate layers of sand and gravel of various 
sizes. The pebbles are normally well rounded and very rarely either faceted or 
scratched. Angular stones are rare. Although small boulders are carried by ice 
cakes and become stranded in the glacial river gravel, large boulders are generally 
absent. 



"Blackwelder, Eliot, Landslide family and its relations (abstract): Pan-Am. 
Geologist, vol. 54, p. 73, 1930. 

Finch, R. H., Mud flow eruption of Lassen volcano: The Volcano Letter, no. 266, 
pp. 1-4, 1930. 

'» Longwell, Knopf, and Flint, op. cit., pp. 77-78. 

~' Blackwelder, EVrot, Glacial and associated stream deposits of the Sierra Nevada : 
California Div. Mines, Mining in California, State Mineralogist's Rept. 28, pp. 306-308, 
1932. 

13 



104 l'LA( i:iv' .MINI.\(i I'OK (lOLl) I.V C'ALIFOKNIA [Bllll. 1:)") 

••'I'.. .Iislii.;;ni-li Ihr .|.|M.sils (.1" :i ;;l;M-ial In. in .-i ii..ii^'l;ici:il lix.T is .lifliciilt 

iiiiil iiriiii iin|M>>.sili|r. iiiilfss • <;iii tr;ni' llic ;;r:n(l lrir:iccs into iictuiil connection 

Willi ;i ul:i.-i:ii I .lin.' ..r ,-,in work nnl in <l.i;iil Ihr phx si,,;;, ;i,,liir hisluiy ,,f tlir 

liistlirl. 

••'rill- (Irposils ni:i<l.' in uhii-i.il lakes aie lallicr disi incti\ o. On lln- liottoin 

of tin- lakr, clay ami sill air laid duwii very cNciily in thin si Is which arc coni- 

inonly Itainlcd as s.-ni lal«r in ci-.,ss-sccl iuii. This is dni> to llic fact llial the layer 
drposiled in winter is finer and riarker in color than the one laifl down dnrin;; the 
Miniiner niellin^' season. Inlike most laki- ileposits the ;,'lacial lake <-lays coinnionly 

contain scattered pel.l.les and even small l.oiilders which have I n dropped from 

cakes of ice lloaliii;: over the lake. These laininaled clays may he associatc-d with 
heds of peat or chalky or dialoinaceoiis earth formed l>y or!,'aiiisms that inhabited the 
i-learer parts of the lake. Si reams entering,' tin; lake form advanciii}; deltas compo.sed 
of ui-ivel and sand in which liie s| rat ificatioii is characteristic of deltas in ;;eneral. 
Ill «|iianlily llie .h^lia dcp,,sil-, ,.licn e.\c4'ed I h<" other lake <leposils fin-atly, for I In- 
glacial rivers carr\ lar;;e ,|iiaiil it ics of coarsi' delriln- all ..f which lod-es in the d.-ltas 
rather than upon the 11 - of the lak.'. 

••Other deposits that may he forimwl in L;laii.ii valleys, such as landslides, tains, 
and alliivi:il fans, lu'cd ii.,t !,.■ descril.cl sp.'cific.illv . 'I'hey ,ire l..cal .iikI ^cifr.illy 
well known." 

Tlie (l('('i)('Miii<i of canyons and llic dt^position of •iiavels by oiitwasli 
si reams wliicli issnc from the snoiils of glaciers form a very important 
chapter in the r(>hl)in,i|- and destrnetion of earlier ^(jld-bearinji' jiravels. 
Much <>[' the material carried by JMeistocene glacial outwash streams 
(,f the Sici-ia Xcvada ^vas diimi)e(l at the foot of the western slope of the 
i-anjic at llic point where ihe major rivers (Milcr the CJreat Valley. The 
extensive ^old-drcdiiiiij^' oi-onnd of California 1o a lar<>-e extent owes 
its existence to these streams. 

So far as the ))rocesses involved in streatn action are concerned, 
mnch can l)e oained by the detailed study of ancient «;lacial stream 
channels fonnd throiifilioiit the world, especially in'its northern belt. 
The mass of literature published on this subject should contribute 
ofcatly 1o the hiiijdiiit:' up of a sysi(Miialic knowledge of stream liabil. 
Physiographic Terms Relating to Streams 

'J'lie mere dednition of some of the tei-ms used in stream ])hysi- 
o<ii-aphy o-ives a dii-ect insioht into the science."'' 

'Cycle of erosiou' includes the sei-ies of ciianp:es from the initial 
cuttino' of a surface to the final reduction of a rejyiou to a baselevel. 
The surface of a rejiion reduced to fairly low relief, but still undulat- 
in<r. is called a '])eueplaiir (also spelled i)eneplane).. It is a si<:nificant 
fact that the Sierra re;:ion in early Tertiary time was aj)pi'oachin<i- the 
pciu'plain stajic of erosion, when the area was covered with lava to 
form a more lU'arly jilain-liUe surface, and later uj)lifted. The uplift 
caused deeji dissection l)y streams. 

Sta<i:es of stream develoi)meiit, from <iulle>s to eom]>letely worn- 
down plains, consist of youth, maturity, and old ape, with continuous 
1 ransil ioiuil sta<,''es between. The early stages repres(Mit very rapid 
jii-owth, which slows down liiadiuilly until at old niic the chanj^cs may 
be extremely slow. 

The «reiH'sis or orioin (,f the stream takes into consiileration the 
initial .surface over which the sti'cam fii'st flowed. Sevei-al tei-ms are 
used by seolo<i:ists in relation to this sub.)ect. (Consequent streams are 
those whose positions were determiiu'd by the initial slopes of the land 
surface. Subsecpient streams are those which are established by orowing 
headward alonp; belts of weak rocks. 

'"Johnson, DouKlas, Streams niul their siKHiticance : Jour, fleologv, \ol. 40, n. 
482, 1S32. 



Sec. II] cKor.odV OK i'i;.\(i;i; i)i;i'()si'rs .jiakins 305 

WlioiT the uiul(M-lyiii<x stniclurcs of llic recks have affected tlie 
(lii-oetioii of tlie stream and its vjdley, llie stream is siiid to luive struct m';d 
eonti-ol. The terms faidt, joint, strike, anticlinal, sviiclinal, ;ind nioiio- 
elinal are prefixed to the -word 'valley'; thus, fault-valley, st i-ikc-vaHcy, 
etc. It is esj)eeially si^'nificant that tlie richest «i'ol(l-beai'in^- channels 
have structural control — the streams oi-i«iinaily ran on <nid aloii^' min- 
ei'alized zones in bedrock. 

Streams may start theii- coui'ses over one sort of <:eol()^ic;d foniui- 
tiou, but as time pro^'resses they ma\' cut thi-ou^h it and be let down on a 
lower and entii'ely (litferent type of structnire; such streams are s;iid to 
lie 'supei-imposed ' (or simply superposed) on the underl>in^' rock struc- 
ture. When a certain stream ])attei-n, originally devcloix'd because of 
pi-evious topo^raphif or struct iiral conditions, is retained even ;if1ei- those 
conditions are removed, the sti-eani is said to Iwive inliei-ited its ix'cnlinr 
features from much earlier jieriods of its life. 

Streams may be intermittent or iiermanent. Depression of topoj^- 
raphy along a coast may cause the sea to invade the valleys, and the 
sti'eams are drowned. T'jn-ise nlonu' the coast may leave han<ii:ing valleys. 
Tributaries to a main stream -which has been much fastei--cutting may 
also be left 'hanpinfr'; as, foi- example, in Yosemite Vall(\v where the side 
streams reach the Merced Kivei- by way of beautifid watei-falls. 

The lonjiitudinal profile of a stream is taken from its source to its 
mouth, -while its gradient represents its inclination at some particular 
part of its course. Ti-ibutaries are said to be accordant Avhen 
at about the same level as their main stream. A stream is sa 
<ii-ade when rate of degradation and rate of aggradation 
equal. 

A stream which is able to maintain its course, even when a segment 
of the earth is gradually raised atlnvart that course, is called an ante- 
cedent stream. If, however, the uprise of the mountain causes the flow 
of the streams to be accelerated down its slope, so that they cut deeper 
gorges, they are said to be re.iuvenated. Even stream meanders, 
developed on a plain, may be entrenched or incised deeply, to form a 
winding canyon by elevation of the plain. 

Rejuvenation may be efTected in other ways than mountain-making. 
Change of climate may make a decided change in stream cutting. 
Stream piracy is another im])()rtant cause. This consists of the cajiture 
of one stream by another. The second lies at a lower elevation ; its head 
cuts back until the first is tapped, oi- beheaded. Then the water frf)m 
the first stream, from that point ui)ward, is caused to flow into the cap- 
turing sti-eam. In this maimer the flow in the first is accelerated often 
to such an extent that a new gorge niay be formed. Whole stream 
systems may thus be readjusted and repeatedly go through new life 
cycles. Piracy and stream a<ljustment were a])parently very active in 
tlie Sieri-a Nevada during Tertiary time; this ]irocess partly accounts 
for many of the deep accumulations there of Tertiary gravel. 

The pattern of an individual stream, or of the -whole or any ])art 
of its system, develops in its own peculiar way bcn-ause of c(M*tain con- 
trolling geological, topographical, and climatic features. The i^attern, 
therefore, is a chJiracter significant enough to bear special study and to 
snpport many new descriptive terms. It is now best studied by means 
of aerial photographs, though detailed t()pogra])liic and geologic maps 
once presented the only bases of accnrate expression. 



thev 


ent 


er 


id to 


be 


at 


are 


abo 


ut 



196 



PLACER MINING FOR GOLD IN CALIFORNIA 



[Bull. 185 




Fig. 72. Diagrams to illustrate three successive 
stages in stream piracy. Tiie stream cutting back at the 
lower elevation beheai/s and captures the stream flow- 
ing at a higher level. After BhickucJdrr and Bmroiis, 
Avierican Book Co. 



Sec. II] GEOLOGY OF I'LAfEK DEPOSITS — JENKIXS 197 

Manj' clues as to the geologic structure and history of the underlyin*'- 
region are gained by the study of stream pattern, from either an intensive 
or regional point of view. In the northern Sierra Nevada, the stream 
pattern developed jirior to volcanic activity was structually controlled 
by bedi-ock; but during the hiter period of vok-anism it sufi'ered cliange 
by that widespread activity. Tlie nuijor streams subsequent to volcanism 
followed the slope of tlie lava-covered, tilted, and uplifted fault-block- 
range. 

An instructive outline of the subject of stream pattern is given by 
Zernitz.'" who desci-ibes and illustrates by many actual examples su<-h 
patterns as follows: dendritie. trellis, i-ectangular. ainiular, radial, and 
parallel. He states that : 

"Tlio pjifti'i-iis wliirli strciiins form .-irc (Ictcnniiicd l)y iiipquiilitics of surf:icf 
slop*' and inoqn.-ilitifs of rock rosistiiiuH-. This Ijciu^- true, ir is ovidcnt th:U draiii.ifif 
patterns may rcflcot orifiinal slope and oriu.ina] strneture or the successive episod<'s 
l»y which the surface has been modified, inclndiiij: iiiilift. depression, tiltinj;, -warpinir. 
folding. fauUinj;. and jointinjj. as well as deposition by the sea. glaciers, volcanoes, 
winds, and rivers. A sinjrle draina.^'e pattei-n may be the result of one or of several 
of the.se factors." 

The fact that lakes fill dein-essions, basins, and valleys along stream 
courses, and that their deposits are intimately associated with those of 
streams, makes their study interrelated with that of stream channels. 
The so-called 'pipe-clay' deposits, which nearly always immediately 
overlie the gold-bearing gravels, represent beds of silt and finely divided 
volcanic ash, which have .settled in lakes and formed a series of thin 
layers. They often contain impressions of leaves, showing the character 
of the forests that grew in that early period. This feature indicates 
that before the volcanic flows came to cover them up, the stream valleys 
had been transfornuHl into lakes, into which the volcanic ash settled. 

In general, a lake is not as long-lived as a stream. Streams tend to 
destroy lakes, either by gradually filling their basins with detritus or by 
cutting down their outlets to a point where their basins may be drained. 
Sometimes, however, lakes persist long enough so that the area whose 
drainage they receive is worn down to a local and temporary baselevel. 
Lakes are formed in a uumber of ways: by landslides across stream 
courses; by lava floAvs which dam up the drainage ; by the down-faulting 
of segments of the earth which are then filled with water; by glacial 
action, either by scooping out rock basins or by danuuiug with till ; by 
peculiar action of rivers themselves, such as silting otf oxbow loops in a 
meandering course. An excellent paper written by the late Dr. W. ]\I. 
Davis has recently been published, which not only discusses the present 
lakes of California.'^ Imt the origin of lakes in general. 

Desert Processes 

In the desert, the processes of erosion and of stream action differ 
very much from those in more humid areas. Only quite recently have 
the geologic processes in the desert been given much consideration ; so 
also has much serious thought f)idy lately turned toward the possible 
development of desert placei-s on a larger scale than mere 'dry wash- 
ing.' The fact that adequate supplies of water may iLsually be derived 

"Zernitz, Kniile, DrainaKe patttins .iiid tbcii- sif,'i!ificanoe : Jour. Ceolngj-, vol. 1.'., 
p. 498. 1932. 

™ Davis, William Morris. The lakes of ( •alif..rnla : California .lour. :\rines and 
Geology, vol. 29, pp. 175-230. 1933. 



108 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 




Fig. 73. A, An example of dendritic drainage pattern, which develops where the 
underlying rocks lie in a horizontal iiosition and offer uniform resistance to erosion. 
After Zernitz, Jour. Geoloyy, 1932. B, An example of trellis drainage pattern which 
develops in folded rocks differing in degrees of resistance to erosion. The stream 
courses are therefore structurally controlled. After Zernitz, Jour. Geology, 1932. 







e It I* 



Fig. 74. Map of southeastern margin of San Joaquin Valley showing funs built 
by streams which disappear after leaving their mountain canyons. The coalescing 
alluvial fans form in this manner an extensive bajada. After Slichter, U. S. Geol. 
Survey Water-Supply Paper 67, 1902. 



Sec. TT] 



(iKOIiOdV Ol' I'LACKU I)i:i'()Sl' 



190 





Fig. 75. A, Block diagram illustrating Cretaceous Sierra Nevada topography. 
The upturned edges of bedrock controlled the drainage pattern, wliich was later 
inherited by streams of the early Eocene period. After Matthes, U. .S. Geol. Survey, 
Prof. Paper 160, 1930. B, Block diagram to show the tilting of the Sierra Nevada 
and its effect on stream cutting.' Erosion, prior to the tilting, planed down the sur- 
face and exposed the granite, leaving only occasional fragments of the intruded 
metamorphic rock bodies as roof pendants. The streams, at the point where they 
leave their mountain canyons and enter the Great Valley, form alluvial fans. After 
Matthes, U. S. Geol. Survey, Prof. Paper 160, I'J.SO. 



^^f^x^~r 




^^^>^:^B)t D. . N R,0 C k^ .^:\J A-S \EyR.\r-;E\S\ Va V-rvC'-/-- 



Fig. 76. Diagrammatic geologic cross-section of Table Mountain in the vicinity 
of Columbia, Tuolumne County. The following principal geologic events affecting 
the ancient channels of the district are graphically illustrated : (1) An early Tertiary 
surface, developed on bedrock over which flowed the old river system of the Cplum- 
bia basin. (2) This surface, including its rich gold-bearing gravels, was later covered 
with lake sediments ('pipe-clay') consisting of fine silty volcanic ash. (3) Ande- 
site 'cobble-wash' then covered the entire country. (4) A canyon was cut in this 
andesite mudflow. (5) A basic lava (latite) flowed down this canyon as a molten 
stream. (6) After this lava cooled and hardened, it became the bed of another river 
which deposited some gold-bearing gravels on its surface, washed from the surround- 
ing eroded region. (7) Continued erosion during tlie Pleistocene resulted in the wash- 
ing away of the less resistamt volcanic materials, leaving the very resistant latite 
standing as Table Mountain. Furthermore, the earlier prevolcanic bedrock surface 
was uncovered, or resurrected, exposing the gold-bearing gravels originally deposited 
in the Columbia channel system. (8) Quaternary erosion has cut canyons of great 
depth, far below the level of the former Tertiary surfaces. 



200 PLACER MINIXG FOR GOLD IX CALIFORNIA [Bull. 135 

from uiulery:rc)uiul sources in the desert, and the fact that tliese sources 
may be found throup-h {reolofrical investij^ation and peophysieal survey- 
ing;, are prradually beinp: accepted. 

Tlie most sijrnificant results of recent desert-process studies are 
sunnnarized by lilackAvehler "^ as he describes the five distinct types of 
desert phi ins: 

1. rfdiinfiits (iiioIiuliiiK tlmse only thinly venoi-rt'd with iilluvial fans), which 
ri'i'iosont the desert slope, cut in bedrock, in contrast to the built-up thick 
alluvial fans or bajadas. 

"reilinients are essentially cuniiinimd ;:ra(le(l flondplains excavated by 
ephemeral stn-anis * * * ii,,. pediment, not (lie ba.jada, is the normal and 
inevitable form (levelo|)ed in the arid re^cions under stable conditions." 

2. Bajadas'*' (compounded alluvial fan.s), which are built iip largely as a 
result of disturbed or interrupted development of fjraded .slopes. The upward 
movement of a fault block causes renewed erosional activity, and thick 
gravel deposits are formed by the conse(iuent titrrents and mudflows when 
thoy are rele.i.sed from their canyons and enter a region of lesser gradient. 

3. Dried-tii» lake bottoms of the desert, or playjis, whose conditions indicate that 
once more i)ermaMeMt lakes tilled the flats and were fed by streams that are 
now nonexistent. 

4. Dip sloi)es, which are broad planes develoiied on a denuded, hard, flat-lying or 
gently tilted rock layer. 

5. River floodplains, which are abnormal desert features, but which were 
apparently more widespread at an earlier time, when precipitation in a given 
region was much greater than it is today. 

These earlier plains and stream courses have been covered b}- the 
bajadas of today, so that the older channels have become buried in the 
true sense of the word. Some of them may represent a large potential 
placer reserve, but they have not yet been well investigrated. 

Need for Establishment of Working Criteria 

From the study of the complicated life history and habit of streams 
and the jiroco.sses involved in their development, a series of working 
criteria should be developed by the exploration geologist for inter- 
preting the conditions found in the deposits of all streams, including 
those of Tertiary age in the Sierra Nevada. There is no text available 
that completely covers all phases of streams — their life history, habits, 
deposits, etc., especially as this study is related to ])lacers, but the subject 
offers an interesting field of research which would have a very broad 
economic application. 

Geologic Conditions in the Gold Provinces of California 
In the Sierra Nevada and Klamath ^Mountains of California gold- 
bearing quartz veins are generally found in metamorphic rocks not 
more than a few miles, at the most, from int)-usive bodies of granitic 
rocks. The age of the metamorphics, which are made up of slates, schists, 
limestones, and meta-igneous bodies, is earlier than Cretaceous, namely 
pre-Paleozoic, Paleozoic, Triassic, and Jurassic. The time of intrusion of 
the granitic masses was late Jurassic. 

The quartz veins were formed shortly after the igneous intrusion, 
during the last stages of the Jurassic. It w(mld seem that the meta- 
morphic rock masses were uplifted and intruded by molten magmas 
which then cooled and contracted, causing the surrounding and over- 

™ niackweUler, Kliot, Desert plains : Journ. Ceolotry, vol. Sit, pp. l.TS-l 40, ]!t.31. 

**' Tlie luiMie h(i)uda placer as adopted somewhat erroneously by Webber and previ- 
ously descrilied in this paper, refers more to single alluvial fans rather than to these 
compound forms. 



See. II] GEOLOGY OF PLACER DEPOSITS — JEXKIXS 201 

lying roof-rocks to craek along many planes of -weakness and to form 
thousands of fissures. Into these openings the residual gaseous solu- 
tions, released from the crystallizing granites and composed largely of 
silica, were injected These, after solidifying, were crushed again, and 
solutions containing gold entered the complex mineralized zones, enrich- 
ing especially the cross-fi-actnres where openings were most abundaht. 

The gold-bearing veins thus formed deep beneath the surface of the 
earth, had then to be brought to the light of day by the erosion and 
removal of the covering layer of rocks, nearly two miles in depth. 
This gigantic work was accomplished during tlip Cretaceous period, and 
as a result thousands of layers of shales, sandstones, and conglomerates 
several miles in stratigraphic thickness were laid down in an adjoining 
marine basin. Some of these beds — especially the last ones to be deposited 
— are gold-bearing, showing that the last part of the Cretaceous erosion 
finally reached the hidden veins. 

That part of the geologic history, however, which was most important 
so far as the making of rich placer deposits is concerned, was the Eocene 
period. The deep erosion which took place during the Cretaceous had 
worn the surface down to such an extent that the metamorphic rocks 
with their mineralized zones had been reached, so that the streams of the 
Eocene ran along and through them. 

Structural control of the drainage, fully developed during the 
Cretaceous, was thus iidierited by the Eocene streams. Ridges and 
valleys followed the north-south trending beds of hard and soft rock. 
The subtropical climate of the early Eocene together with other condi- 
tions particularly favorable to rock disintegration, such as a more pro- 
longed time of stability in the earth's crust, made it possible for the gold 
in the surface rocks to be released from its matrix. 

Then came the inception of the Tertiary Sierran uplift, which 
rejuvenated stream flow, causing the released gold in the disintegrated 
veins to be washed into the river channels, resulting in very rich con- 
centrations. The streams were loaded with fine quartz sand and pebbles, 
together with clays derived from the decomposed feldspathic parts of 
the rocks. The finer particles were washed to the sea, and as a result 
the Eocene (lone formation) today contains large deposits of com- 
mercial clay interbedded with quartz sands. 

The westward tilting and resulting acceleration of stream flow 
interrupted the north-south drainage system inherited from the Creta- 
ceous period. The readjustment of the streams resulted in their general 
direction of flow being finally changed from north and south trends to a 
w^esterly course, somcAvhat as it is today. The longest of these known 
streams even headed far to the east into what is now Nevada. 

Hardly had the Eocene come to a close when much rhyolite ash, 
thrown into the air from volcanoes, settled over the region. By Oligo- 
cene time, rhyolite ash had covered much of the northern Sierra Nevada, 
damming rivers and forming lakes, the bottom sediments of which are 
now represented by thinly layered pipe-clay immediately overlying the 
richer gold-bearing gravel. The newly developed rivers, flowing directly 
down the western-tilted slope of the Sierra, over a volcanic cover, as 
consequent drainage, were repeatedly interrupted by continued ejections 
of lava and a further tilting of the region. Not until the late Pliocene 
or early Pleistocene diet the constant out-pouring of lava cease. Then, 



'J()2 



PLACER MININ'O FOR OOLD IX CALIFORNIA [Bull. 13.' 




^^^^ 









n- 



Fig. 77. Aerial map (for explanation, .see fig. 7 8 caption). 
Photo by courtesy of Fairchild Aerial S^irveys. Inc. 



Sec. II] 



GEOLOGY OF PLACER DEPOSITS — JENKINS 



203 




Bed A'ocA- 




Fig. 78. Index sketch (reduced) of the same area shown in figure 77. Explana- 
tion of figiire 77 : Mosaic made up of many overlapping vertical photographs taken from 
an airplane, elevation 10,000 feet : area 6 J by 4 miles, between Jamestown and Angels 
Camp on the Mother Lode (see fig. 78). The Stanislaus River winds through the upper 
half of the picture ; in the lower, the Table Mountain latite flow, which occupies a late 
Tertiary canyon cut in andesite 'cobblewash', stands oi t in bold relief. The softer 
andesite rocks and the underlying 'pipe-clay' cut by this canyon have been stripped away 
by Pleistocene erosion, save for two or three small patches remaining in protecting 
curves of the harder lava flow. The surrounding country lies lower than Table Moun- 
tain in elevation, and is worn in bed-rock. The prevolcanic gold-bearing channels are 
represented only as gravel-filled fragments, which, however, show their northward 
trend, parallel to the strike of bedrock and the Mother Lode. These remnants can be 
recognized in the pictures only after field examination. One such mined-out channel 
passes under Table Mountain at right angles to it, near its central position in the 
picture. It was here that the Humbug drift mine on the south met the New York tunnel 
on the north, resulting in an underground fight, and later litigation. 



204 



PLACER MINING FOR GOLD IN CALIFORNIA 



[Bull. 135 







■^ 








.■-i<?-. 


ii^h. . .JUy 




•?■•, 




^^9^. ' v^^ 


=*^'^:' ■-- 


^:"-*^ 


=^il^ 










■' '-(^ 






gi^iii 


i ■. 


\ 


^■^J^:^ 


^-j^' 


^ iSittR' 




fr-- 


mm» 


mmM 



Fig. 79. Surface of the resistant Table Mountain Uiliic la\u llow which once 
filled a canyon cut by a river in andesite 'cobble-wash'. Later the latite surface 
served as a stream bed: now it is the flat mountain top in Tuolumne and Calavtras 
Counties referred to in the writingrs of Mark Twain and Bret Harte. Cut by courtesy 
of Engineering and Mining Journal. 



by a series of violent earth movements, the Sierra Nevada broke away 
from the region to the east along huge fault-scarp.s, which are formed 
at the foot of the present steep eastern slope, where displacements are 
now measured in thousands of feet. Within the Sierran slope, smaller 
adjustment faults also broke the continuity of the older buried Tertiary 
stream grades. Some of the ancient streams, the courses of which headed 
farther to the east, were virtually 'cliopped' into many pieces ; some were 
elevated and others depressed, and many were warped to various peculiar 
positions. Undoubtedly there are some segments of these old channels 
which now lie deeply buried beneath great tliicknesses of alluvium in 
down-dropped fault-blocks east of tlie Sierran escarpment. 

In the Great Basin and the Mojave Desert region of California and 
Nevada are remnants of Tertiary stream deposits, interbedded with or 
lying beneath lavas, all of which have suffered nnich by faulting and 
warping. 

In these regions, however, the most important period of placer 
formation was in the early Pleistocene, rather than in the Tertiary, 
Two types of lode gold supplied the sources. One type was formed in 
much the same manner as the Sierra Nevada lodes. The other consisted 
of mineralized zones in rhyolite of early and middle Tertiary time. In 
the Pleistocene there were normal streams flowing through the desert, 
fed by melting glaciers of the higher mountains. Placers that were 
formed by these Pleistocene streams have since been largely covered by 
desert alluvial fans. Some have been elevated and are cut by more 



Soc. ir 



fiKOIiCKiY OF PLACER DEPOSITS — JENKINS 



205 




Fir.. SO, Ideal crdss-sr,- 


liun of a 


ri\rr in tl 


H Sierra Nevada 


the bed of wliieh 


lias suffered down-faultiiipr on 


tlic ui.st 


ream side 


causing gravels, 


sand, and silt to 


ai'cumulate in the pocket thus 


formed. 









recent streams, -when present in this arid region, so that recent concen- 
trations from older river gravels provide one source for the desert dry 
placer. 

In the Klamath Mountains, though the early geologic history was 
much like that of the Sierra Nevada, there were no lavas to fill the valleys 
in which the stream gravels were deposited. Uplifts, accompanied by 
renewed stream-cutting, caused terraces to be left on the valley sides, 
where the rich gravels have given up their gold to hydraulic mining. 
Some of the finer gold particles were washed by the rivers to the sea 
and have formed deposits known as beach placers along the northern 
shore of California. 

Down-faulting of various degrees of magnitude in places caused 
accumulations of gravels to form, especially on the down-throw sides of 
faults. A number of such faults are located in both the Sierra Nevada 
and Klamath Mountains, and may hold a reserve of gold not yet entirely 
recovered. In the Sierra most of these minor displacements show that 
the east side of the fault-plane has been dropped down, so that where 
faults cross westward flowing rivers, accumulations of gravels have taken 
place in pockets thus formed, east of the fault-plane and upstream. 

The whole Pleistocene period was one of great events for California. 
The eastern side of the Sierra Nevada was raised to very lofty heights. 
The westward-flowing streams, as a consequence, were so greatly accel- 
erated that they cut deep and rugged canyons. The uprise, accompanied 
by faulting, caused such violent earthquakes that enormoiLs masses of 
rock were shaken from the mountain sides, in many places to form local 
lakes which were later to be drained and destroyed by active erosion. 
Glaciers developed in the higher mountains and crept down the canyons, 
carving them wider and leaving them U-shaped in form. Their melting 
supplied much w'ater to the streams. Some local volcanic cones were 
built up here and there near or over the fault planes. 

The Tertiary stream gravels, which had long been buried deeply 
beneath lavas, were exposed by the Pleistocene canyon-cutting rivers. 
From the dissected portions of the old channels, gold was removed and 
washed into the newer streams, which concentrated it on their bedrock 
riffles. The remaining portions of the Tertiary deposits were left with 
their stubs exposed high up on the intervening ridges. In places, 
erosion merely stripped the covering of volcanic tuffs, sands, and 
gravels from the bedrock, leaving the channel with its rich gold deposits 
laid practically bare for the lucky earlj- miner to win. Some of the 
finer particles of gold w^ere swept clear out to the Great Valley where 



Q) 



206 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

they were dropped on the edj^^e of the i)laiii. These areas ai-e now the 
dredge grounds. 

The general western tilt of tlie Sierra Nevada has been found to 
eontinue along the same slope (about two degrees) far beneath the 
alluvium and sediments of tiie Great Valley. Areas dredged for gold 
values in the gravels thrown down by tlie great canyon-cutting rivers 
of the range lie along the extreme western margin of the foothills near 
the place where bedrock passes beneath the alluvium, and aligned in a 
direction N. 20° W. The gravels dredged do not lie directly on bedrock 
but on tuffaceous clay layers, spread out above the detritus-covered 
down-warped iSierran surface. Beneath the 'false-bedrock' and cut 
in the true bedrock surface is a stream pattern with gold-bearing 
gravel-filled channels, now reached only in one or two places. This 
buried channel system undoubtedly holds in reserve a great wealth for 
future improved exploration and development. Excessive underground 
water is ahvays encountered in these mines which are located beneath 
the level of the alluvial plain. 

The great differences between the geology of the Coast Ranges and 
that of the Sierra and Klamath regions are fundamental in that the 
western area served frequently as a basin for deposition during the 
Tertiary and Cretaceous, while the latter represented land areas through- 
cut that time. The Coast Ranges together with the Great Valley now 
contain enormous accumulations of marine Tertiary and Cretaceous 
sediments, while the Sierra Nevada and Klamath IMountains are not 
so covered. Cretaceous and Tertiary streams coursing down the moun- 
tain flanks brought gravel, sands, and clays into a marginal sea. 

The very fact that streams are conveyors of materials, in contrast 
to the basins of deposition toward which they i\o\\', accounts for the 
very different geologic conditions on the two sides of the Great Valley. 
Certain geologic time divisions of the Cretaceous and Tertiary of the 
Coast Ranges are represented by strata measured in ma)iy thousands 
of feet, while in the Sierra mere films of Tertiary gravels, or deposits 
of no greater thickness than a few hundred feet, trapped by volcanic 
coverings, represent some of these same later periods. Particles of gold, 
recurrently washed from the mineralized rocks of the mountain range, 
were dropped, b\^ reason of their high specific gravity, and retained in 
the bedrock riffles of both the ancient and modern streams, while the 
lighter detritus was carried to the broad sea basins to form strata cover- 
ing hundreds of square miles. 

Conclusion 

The depletion of the more accessible and more easily discovered 
gold i)lacers, followed by lo.sses due to poorly directed exploration, 
calls for a more effective technicjue to bring further success to placer 
mining. The techni(iue is available; the next thing to do is to apply it. 

First, there is aerial photograph}' which may speedily and accu- 
rately give a wealth of valuable information as regards geology, and 
in addition, the finest sort of a map showing surface features in 
greatest detail. 

Second, there is geophysical surveying which, when coordinated 
with geology, may greatly aid underground prospecting in making new 
discoveries and in reducing its cost by more intelligently directing its 
course of action. 



S(V. 11] GEOLOGY OF I'LACKH DEPOSITS — JENKINS 207 

Tliird, pli3-.sioyTai)liie ^eoloj^y, advanced to a more systematic 
science than ever before, may be nsed in unravelling the history of the 
ancient streams and their corresi)oiuling topography. Contouring the 
predava surface is found to be an excellent method of showing graphic- 
ally this ancient topography, and especially the old valleys in which 
la\' the early gold-bearing streams. 

Fourth, a better understanding of desert processes in general and 
desert placers in particular should help to develop a gold reserve which 
has so far not received the attention it deserves. 

PMfth, the technique recently developed in the examination of 
stratified sediments, their structure, texture, mineral-grain composition, 
etc., may be aptly applied to placers, to aid in tracing out their origin 
and the cour.ses of the older drainage systems noAV extinct. 

In taking stock of the possible reserves of placer gold in Cali- 
fornia, several sources would seem worth investigating. All of these 
require detailed exploration prior to any attempt at mining. For the 
most part, these reserves are buried or concealed in such a way that 
they have either been overlooked or considered too remote or too much 
of a speculation for a mining venture. Such factors as involved 
water-rights, litigation, difficulty in gaining title, laws unfavorably 
atfecting hydraulic mining, lack of sufficient capital, and many other 
stumbling blocks now prevent good placer ground from being worked. 

The possible reserves discussed in this report may be summarized 
as follows : 

Pleistocene and Recent Placers 

1. Deep river gravel deposits, over which the present larger rivers 
are now flowing. Recent and Pleistocene faulting caused gravel to be 
accumulated on the down-throw^ side of faults, while the rivers have 
(continued to flow over the gravels without washing them completely out. 

2. Pleistocene stream placers, buried beneath alluvial fans of the 
Ch-eat Basin and Mojave Desert. 

3. Recent ephemeral stream deposits and alluvial fans or 'bajada 
placers' of the Great Basin and Mojave Desert regions. 

4. Marine or beach placers along the coast, for the most part 
located in northern California. 

5. Isolated high terraces or bench gravels, such as those which 
occur in the Klamath Mountains. 

Tertiary Stream Placers 

6. Gold-bearing channels cut in bedrock which lie beneath the 
false bedrock layers of the dredged areas along the western foot of the 
Sierra Nevada. 

7. Buried Tertiary channels and associated covered benches located 
in the well-known gold-bearing districts of the state. Large areas still 
lie buried and unexplored in some of the older mining districts. 

8. Buried Tertiary channels and benches in the lava-covered dis- 
trict which lies between the Sierra Nevada and Klamath ^Mountains. 
]\Iost of this area is probably too deeply covered to be reached by 
mining, but the southern marginal area may have some po.ssibilities. 

9. Tertiary channels of the Great Basin and Mojave Desert areas, 
interbedded with volcanic rocks or lying beneath them. 



208 PLACKH MINING FOR HOLD IN CALIFORNIA [BuU. 135 

10. Tertiary iiiai-iiic jjIjuhms. l^'inely divided jrold partic-les in the 
Joiie formation at tlio point wlicrc flie i-oiTcspojKliii'j Eocene streams 
entered the lone sea. 

Cretaceous Marine Placers 

11. Ci-etac-eous marine placers, lar^'oly in the Cliieo conglomerate 
(ri)per Cretaceous) beds of northern California. The Lower C'reta- 
ceous beds are also reported to contain some <iold-bearin<r layers. 

Largest Reserve 

Tiie largest of these possible reserves probably lie in the remain- 
ing bnried Tertiary stream placers of tlie northern Sierra Nevada. 



Bibliography of California Placers and Related Geological Subjects 

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Vol. IS, l'J2<J, pp. :!47-44,S 
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Ancient river-bed deposits in California: Pacific Min. News, Eng. & Min. 
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Geologic chart appertaining to the ancient river beds of California: Cal. 
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Pliysiograpliy and geology of the Siskiyou Range: (Abstract) Jour. Geol.. 
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Jurassic and Cretaceous divisions in the Knoxville-Shasta succession of 
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A great gravel mining enterprise: Min. & Sci. Press, vol. 30, 1875, p. 70. 

The Inter-Yubas ridge: Min. & Sci. Press, vol. 32, 1876, p. 312. 

Placer Countv Minea : Min. & Sci. Pre.ss, vol. 33, 1870, pp. 33, 42, 65, 74. 

The mining intere.sts of 1S70 : Min. & Sci. Press, vol. 34, 1877 (hydraulic 
mining), p. 41. 

Theory of auriferous gravel channels : Min. & Sci. Press, vol. 41, ISSO, p. 226. 

Spring Vallev mine: Min. & Sci. Press, vol. 42, 1881, pp. 441, 452. 

Pocket mining and nuggets: JNIin. & Sci. Press, vol. 44, 1882, p. 190. 

Dredging for gold: Min. & Sci. Press, vol. 45, 1882, p. 24. 

Gravel: .Min. & Sci. Press, vol. 45, 1882, p. 328. 

Measurements of auriferous earth : Min. & Sci. Press, vol. 45, 1882, p. 328. 

The discovery of gold in California: Min. & Sci. Press, vol. 50, 1885, p. 37. 

Auriferous gravel in Placer County: Min. & Sci. Press, vol. 51, 1885, p. 165. 

New placer diggings: Min. & Sci. Press, vol. 55, 1SS7, p. 228. 

River svstem of ralifornia : Min. & Sci. Press, vol. 55, 1S.S7, p. 228. 

Buried trees in gravel mines: Min. & Sci. Press, vol. 02, 1891, p. 339. 

Geology of Placer, El Dorado, and Amador Counties : Min. & Sci. Press, 
vol. 70. 1S95, pp. 308-310. 

California's supposed great rivers of ancient times : Min. & Sci. Press, vol. 77, 
1898, p. 401. 

Prehistoric rivers of California: Min. & Sci. Press, vol. 79, 1899, p.' 544. 

(»1.1 channel jjlacers : Min. & Sci. Press, vol. 82, 1901, i)p. 175-176. 

Cold (Ir.-.lging in California: Min. & Sci. Press, vol. 91, 1905, pp. 125-126, 
141-142, 100-161, 178-179. 

Hydraulic Mining in Humboldt County, California : Eng. & Min. Jour., vol. 79, 



1905, p. 30 



draulicking in Trinity County, California: Min. & Sci. Press, vol. 101, 



1910, p. 143. 

Hvdraulicklng at La Grange Mine, Trinity County : Eng. & Min. Jour., vol. 95, 
1913, pi}. 1005-1007. 

Map of black .sand deposits: Min. & Sci. Press, vol. 118, 1919, p. 264. 

Uniciue placer development. River Placers, Ltd., engaged in unusual project 

on Middle Fork of the Yuba River: Min. Jour. (Ariz.), vol. 14. no. 23. 1931, p. 4. 

Auburv, I.rf'wis E. — (Jold dredging in California: (Introductory) Calif. State Min. Bur. 

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Cold deposits of the Retlding and Weaverville quadrangles: State Mineralo- 
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1882, pp. 845-854. 

Gravel deposits of the lower Klamath : Min. & Sci. Press, vol. 50, 1885, p. 391 



Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 209 

Becker, George F. — Structure of a portion of the Sierra Nevada of California: Bull. 
Geol. Soc. Amer., vol. 2, 1891, pp. 49-74. 

Antiquities from under Tuolumne Table Mountain in California (with dis- 
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The Witwatersrand Banket with notes on otht-r gold-bearing pudding stones : 
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Auriferous conglomerates of the Transvaal: Amer. Jour. Sci. (4), vol. V, 
1898, pp. 193-20S (including notes on California). 
Becker, George F., Lindgren, W., and Turner, H. W. — Description of the gold belt: 
U. S. Geol. Survey, Sonora folio, 41, 1897 ; Bidwell Bar folio, 43, 1898 ; Downie- 
ville folio, 37, 1897. 
Blackwelder, Eliot — Pleistocene glaciation in the Sierra Nevada and the Basin Ranges : 
.Geol. Soc. Am. Bull., vol. 42, 1931, pp. S65-922. 

Glacial and associated stream deposits of the Sierra Nevada : State Mineral- 
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Eastern slope of the Sierra Nevada: XVI Nat. Geol. Congress Guidebook 16, 
Ex. C-1. 1933, pp. 81-102. 
Blake, Theodore A. — Remains of the Mammoth and Mastodon in California: Am. Jour. 

Sci. (2), vol. 19. 1S55, p. 133. 
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vol. 43, 1867, pp. 270-271. 

Note on a large lump of gold found on the middle fork of the American 
River: Calif. Acad. Nat. Sci., Proc. 3, 1868, p. 166. 

1. New locality of fossils in the gold-bearing rocks of California: pp. 289- 
290. 2. Tooth of the extinct elephant, Placer County: p. 290. 3. Quarry of gold- 
bearing rock: pp. 290-291. Calif. Acad. Nat. Sci., Proc. 3, 1868, pp. 289-291. 

On a fossil tooth from Table Mountain: Am. Jour. Sci. (2), vol. 50, 1870, 
pp. 262-263. 

The various forms in which gold occurs: Rept, Director of the Mint, 1SS4, 
p. 573-597 (1885). 
Bordeaux, Albert F. J. — Les anciens chenaux auriferes de Californie : An. Mines (10), 

vol. 2, 1902, pp. 217-258. 
Boutwell, J. M. — The Calaveras skull' (shown to be of recent origin) : U. S. Geol. Survey, 

Prof. Paper 73, 1911, pp. 54-55. 
Bowie, A. J. — Hydraulic mining in California: Amer. Inst. Min. Eng., Trans. 6, 1879, 
pp. 27-100. 

Mining debris in California rivers : Trans. Tech. Soc. Pac. Coast, vol. IV, 
Feb.-March, 1887. 

A practical treatise on hydraulic mining in California: New York (Fifth 
Edition), 1893. 
Bradley, Walter W. — Renewed activity in California gold mining: Min. & Met., vol. 13, 
1932, pp. 385-390. 

Itinerary, Yosemite to Mother Lode: XVI Int. Geol. Congress, Guidebook 16, 
Ex. C-1, 1933, pp. 62-65. 

An echo of the days of '49: Eng. & Min. Jour., vol. 135, 1934, pp. 494-496. 
Brewer, William H. — Alleged discovery of an ancient human skull in California: Am. 

Jour. Sci. (2), vol. 42, 1866, p. 424. 
Brooks, E. F. — Platinum in California: Min. & Sci. Press, vol. 114, 1917, p. 116. 
Brown, C. J. — Hydraulic gold mining: Min. & Sci. Press, vol. 31, 1875, pp. 50, 114, 161, 

178, 313, 316; vol. 32, 187C, pp. 50, 89, 121. 
Browne, John Ross — Report on the mineral resources of the States and Territories west 
of the Rocky Mountains: U. S. Treasury Dept., 1868. 
Resources of the Pacific slope: New York, 1869. 
Browne, John Ross, and Taylor, James W. — Reports upon the mineral resources of the 

United States: U. S. Treasury Dept.. 1867. 
Browne, Ross E.- — The ancient river beds of the Forest Hill divide : State Mineralo- 
gist's Rept. X, 1890, pp. 435-465. With maps, sections, and plates. 

The channel system of the Harmony Ridge, Nevada County : State Mineralo- 
gist's Rept. XII, 1894, p. 202. 

California placer gold: Eng. & Min. Jour., vol. 59, 1895, pp. 101-102. 
Gold in ancient California river channels: Min. & Sci. Press, vol. 77, 1898, 
pp. 107-108 ; (Mysteries of the ancient rivers of the Forest Hill divide, Placer Co., 
CaUf.): vol. 78, pp. 285-290. 
Bryan, Kirk — Geology and ground-water resources of Sacramento Valley, California: 

U. S. Geol. Survey Water-Supply Paper 495, 1923, 285 pp. 
Bush, Edgar — Active placers in southern California: Min. Jour. (Ariz.), vol. 16, 

1932, p. 7. 
Casey, Thos. Lincoln — Mining debris, California: 51st Congress, House of Rep., Ex. 

Doc. 267, 1891. 
Cassidy, Andrew — The California Blue Lead in Oregon and Washington Territory : 

Min. & Sci. Press, vol. 30, 1875, p. 82. 
Chaney, Ralph W. — Age of the auriferou.s gravels: (Abstracts) Bull. Geol. Soc. Am., 
vol. 43, 1932, pp. 226-227; I'an. Am. Geol., vol. 53, 1931, p. 361; vol. 56, 1931, 
pp. 71-72. 

Notes on occurrence and age of fossil plants found in the auriferous gravels 
of Sierra Nevada: State Mineralogist's Rept. XXVIII, 1932, pp. 299-302. 

Further evidence regarding the age of the auriferous gravels: (Abstract) 
Bull. Geol. Soc. Am., vol. 44, 1933, p. 78. 
Chase, A. W. — The auriferous gravel deposit of Gold Bluffs: Am. Jour. Sci. (3), vol. 7, 

1874, p. 379. 
Cleaveland, Newton — Giant gold dredges at Natoma, California: Min. & Sci. Pre.ss, 

vol. 103, 1911, pp. 446-448. 
Crampton, F. A. — .Vuriferous gravel channels in Nevada County: Min. Jour. (Ariz.). 

vol. 16, no. 6, 1932, pp. 5-7. 
Cranston, R. E. — Mechanical features of the California gold dredge : Min & Sci Pre*;s 
vol. 104, 1912, pp. 303-307, 338-342, 372-375. 



210 PLACKK MIMXG FOU COI.I) IN (AI.IFOWMA [r>ull. V.]') 

Cronise. Titus l->v — Tlu- ii:iliir;il woallli ..f ('uliic.niia : II. H. Daiioroft & ("..., San 

Francisco, 1S68. pp. 41(;-4;!;!, .j;U-.'.47. 
Crossniiin, J. M. — AurilViuiis gravels ..I San liabrid Kaniro, San Dti iiarditio <"i.iMily: 

State Mineialunists Ui-pt. IX. lsss-|s>;ii. pp. l-iW-lM. 
David.son, GeoPKc — on thi- anrilVnms uravtl dcpusits of California: Calil'. .\( ail Si i., 
Proc. .'.. 1S7:!, pp. 1-I.")-H«. 

Gravels in Placer (.'ount.v, California: Calif. Acad. Sci., Proc. .'.. 1ST.'., p. 41. 
Davis, Horace — On anrifeious ^rravels near Sonura, California: Calif. Acad. .\at. .Sci., 

Proc. 1, isr..'., p. t;i ; 2d edition, lS7:f, p. di". 
Day, David T. — Platimini : .\Iin. & Sci. Press, vol. 7S. IS'.c.i. p. SS. 

Notes on the occnn-eni-e of platinum in North America: Trans. .\ni. Inst. 
.Min. Eng-., vol. :'.*>, I'.'OO, p. 702. 
Dav, David T., and Richards, K. H. — Useful min<-rals in the black sands ..i ili.- Pa<l(i<- 

slope: U. S. Oeol. Survey, Min. lies. f<ir l!iO."i (1006), pp. 1 17.")-1 2.".S. 
De (^root, Henry — Hydraulic and drift mining: State Mineralogists Kept. II, ls^2, 
pp. i:<3-iyo. 

Recollection of California mining life: Min. & Sci. Press, vol. 47, iss:'., 
pp. 292, :J20-321, 3:!0, :;4G, 3S2. 

The San Francisco ocean placer — the auriferous Inacli sands: State .Min- 
eralogists Kept. IX, \S'.H), pp. 54.".-.'.47. 
De La Rouglisse — Note sur les mines d'or de (Jolden River (California): 4>l pp., 

Paris. ISSr.. 
De Launa\, D.- -( ienlugical d.s. lipliun of tlie ynld min.-s of the Transvaal < Wil wat.-rs- 
rand, Heidell>erg, and Kerksdorp districts) : Trans. Inst. Min. KiiK., v..l. 11, IS'.iK 
(California, p. 4:!4). 

Alluvions auriferes de Californie: In L. De Uiunay. 'I'raile >U- Melal- 

logenie Cites Minerau.x et Metalliferes. vnl. :!. Paris el l.iege. \'.<\'-'-, pp. 7ii.".-712. 

Dickenson. Roy K. — The lone fornialiun of th<- Si.^tia .Vevada footliills, a Incal facies 

of the upper Tejon-Kocene : Science (n. s. ). v.. I. 40. 1!'14, pp. 07-70. 
Diller, J. S. — Notes on the geology of northern California: U. S. Cenl. Survey Dull. :::!, 
1SS6. 

Geology of the Lassen Peak district : V. S. Geol. Survey, ^th An. Rept., ISS'.I, 
pp. 39.J-432. 

Geology of the Taylor.-ville r.-ui-.n <■( California: Dull. C.nl. .v,,,-. .\ni.. vl. :!, 
l.S!i2, pp. 369-304. 

Cretaceous and earlv Tcrtiarv <>( nortliern Califurnia ami Oregon : Pull. Ct-nl. 
Soc. Am., vol. 4, 1893, pp. 203-224. 

. . . on the auriferous gravil 
ville, California: Am. .lour. Sci. (:{). 

Revolution in the tnpography of t 

period: Jour. Geol. vol. 2, 1S94, pp. ,iL'- 

Tertiary revolution in tlie topofii 

vey, 14th An. Rept., pt. 2. 1S94, pp. 1 

La.ssen Peak folio (.\o. 1.-. ) : P. S 

GeomorphogiMi.v of the Klamail 

Bull. 12. 1901. p. 4C1. 

Topographic development of tin 
Bull. 196, 1902. 

Mineral resources of the Indian \'all«\- legion. California : P. .'>. Geol. Survey, 
Bull. 260, 1904, pp. 4.'>-49. 

Redding folio (No. 13S) : U. S. Geol. Survey, lOdil. 

Geology of the Taylorsville region, California: P. S. Geol. Survey, Pull. :!.".:'., 
lOOS, p. 12S. 

The auriferous gravels of the Trinity River Basin, i 'alifoi iiia : P S. CiiiA. 
Survey, Bull. 470. 1911, i)p. 11-29. 

Trinity River gravels, California: f:ng. &; Min. Jour., vol. 92, P.' 1 1 , pp. 
495-497. 

Auriferous gravels in the Woaverville quadranele, California: P. S. Geol. 
Survey, Bull. r.40, 1914, pp. 11-21. 
Dolbear. S. H. — Dry plac.r mining in California: Eng. <Ji -Min. ,Iour., vol. S9. 1910, p. :;.-|9. 
Donnelly, Maurice — Geology and mineral deposits of the .lulian district. San Diego 
County, California: State ^lineralogist's Rept. XXX, P.i"4 (plae.r deposits), 
p. 309. 
Do<,little, J. E. — Gold dredging in C.ilifoi nia : Cal. Stat." Min. Pur.. Bull, .-.fi, 19(i:,. 
Dragaje de oro en California: Bol. Soc. Nac. .Min. CI), vol. IS, 1907. pp. 
409-428. 
Dr<jn, R. W. — Gold mining in the Sieira .Nevada, California: ibol. Soc. Glasgow, 

Trans. 11, 1900, pp. 203-206. 
Diiling, John F. — Geoph^•sics as an aid in gold ])lacer iltilt mining: .\lin. Jour. (.\ri-/..), 

vol. PS, Mar. 30, 1933. pp. .'. •;. 
Dunn, R. L.— Drift mining in C.ilifornia: State .Mineraloni.-fs It.pt. N'lII. isss, i.p. 
736-770. 

River mining: State .Miueralonisfs Rept. IX. IS'.mi, pp. 202-2^1. 
Aurifi'rous conglomerate in California (Siskiyou Coiintv) : State .Mineral- 
ogists Rept. .XII, lS93-l.S!i|. pp. 4.".:t-471. 
K<lil.\. L. H. — Dredg.-s on uppei Ameriean River: Kng. iVl Min. .I..ur., vol. '.i:;, pil2, 

pp. 997-1(100. 
Edman, J. A. — .Votes on the gold hearina hhu'k sands of Califoniia : .Min. iVc Sel. Pr.ss, 
vtd. 09. l.sy4, pp. 291. ;!3ii. .■;72. 

Platinum minerals of Pluma> Co , California: .Min. .<: .Sei. Piess, vol. 77. 
1S9S. p. 4(»1. 

The auriferous l.la<-k sands of California: Cal. State Min P.ur. Pull. 4.", PMi7. 
pp. 5-10. lOng. \- .Mill. J.iur., vol. >:!. 1907, pp. Hi47-ln4s. 
Lflner. A. E. — Beach mimng with surf washer: .Min. & Sci. Press, vol. 80, 1903, p. 304. 
Egleston, T— The lorinaiion of yohl nuggets and placer deposits: Trans.. ,\mer. Inst. 
.Mm. Eng., vol. 9, ISsi, pp. i;33 (146. 

, oo ^^'o'l^i'iP placer ileposits in the United St.ites : School Minos Quart., vol. 7, 
1S86. pp. 101-131. 

Diift mining: S.hool .Mines (Juart., \ol. S. 1SS7, pp. 201-220. 



nortliern California ami ( >! 


•enon : 


Pull, t 


of lacustral origin in the r 


egion < 


-f Tayl 


Vol. 40. Is9:',. ))p. :','.'^— :!'.i9. 






tile Pac'ific Coast since tlie : 


a mile) 


•OUS '^V 


-3 4. 






■aphv of ih.. Pacili<- eoast : 


U. S, 


(iiiil. ; 


o;;-4:;:;. 






;. G. oi. SuiM '■. ]s'.<r,. 






Ii .Mountains; (Alistracl) 


Geril. 


S..C. . 


• Klamath Mountains: P. 


S. Gt 


•ol. Sui 



Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 211 

Ellsworth, Elmer W., Tracing burled-river channel deposits by geomagnetic methods: 

State Mineralogists Kept. XXIX, 193H. pp. 244-200. 
Endlich, P. M. — Mining in the Mojave Desert in California (Goler Dry Placers) : Kng. 

& Mln. Jour., vol. G2, 1896, pix I'JT-l'JS. 
Eteson, A. C. — Suggestions on inland gold dredging: Min. & Sci. Press, vol. 81, 1900, 

p. 597 ; vol. 82, 1901, p. 36. 
Fairbanks, Harold W. — Geology of the Mother Lode region : State Mineralogist's 
Kept. X, 1S90, pp. 23-90, map. 

Red Rock, Goler, and Summit mining districts in Kern County : State Min- 
eralogist's Rept. XII, 1893-1894, pp. 456-458. 

Auriferous conglomerate in California: Eng. & Min. Jour., vol. 59, 1895, 
pp. 389-390. 

Red Rock, Goler, and Summit mining districts in Kern County : Min. & Sci. 
Press, vol. 70, 1895, pp. 241, 245. 
Ferguson, H. G., and Gannett, R. W. — Gold quartz veins of the Alleghany district, 

California: U. S. Geol. Survey Prof., Paper 172, 1932. 
Foster, G. G. — The gold regions of California: New York, 1848. 
Franke, Herbert A. — Selected bibliography on placer mining: State Mineralogist's 

Rept. XXVHI, 1932, pp. 219-224; XXX, 1934, pp. 283-289. 
Fuchs, Edmond — Note sur les graviers auriferes de la Sierra Nevada de California: 

Soc. Geol., France, Bull. (3) 13, 1885, pp. 486-488. 
Fuchs, Edmond, and de I-aunay, L. — Alluvious aurlf6res de California: In Trait6 des 

Getes Mineraux et M^iallif^res, vol. 2, Paris, 1893, pp. 961-969. 
Gardner, E. D., and Johnson, C. H. — Placer mining in western United States: U. S. 

Bur. Min., Inf. Cir. 6787, 1934, pp. 1-89. 
Gibson, Arthur — Magnetometric determinations applied to placer mining: Eng. & Min. 
Jour. Press, vol. 114, 1922, pp. 1064-1069. (California.) 

Auriferous placer resources of California: Min. Cong. Jour., vol. 13, 1927, 
pp. 476-479. 
Gilbert, G. K. — Stages of geologic history of Sierra Nevada: Wash. Phil. Soc, Bull. 9, 
1887, p. 7. 

Terraces of the high Sierra, California: (Abstract) Science, (n.s.), vol. 21, 
1905, p. 822. 

Transportation of detritus by Yuba River: (Abstract) Bull. Geol. Soc. Am., 
vol. 19, 1908, pp. 657-659. 

Quantity of mining debris: U. S. Geol. Survey, Prof. Paper 73, 1911, pp. 
18-21. 

Hydraulic mining debris in the Sierra Nevada: U. S. Geol. Survey, Prof. 
Paper 105, 1917, 154 pp. 
Gledhill, Edward — The analogy between the gold "cintas" of Colombia and the aurifer- 
ous gravels of California: Trans., Inst. Min. Eng., vol. 20, 1902, pp. 391-400. 
Goldstone, L. P. — Fresno, Sierra, and Tuolumne Counties: State Mineralogist's Rept. X, 

1890, pp. 734-738. 
Goldsmith, E. — The blue gravel of California: Acad. Nat. Sci., Phila., Proc. 1874, 

pp. 73-74. 
Goodyear, W. A.-^The auriferous gravels of California: Min. & Sci. Press, vol. 39, 1879, 

pp. 182-183. 
GrifHn, F. W. — The gold dredging industry: Mln. & Sci. Press, vol. 88, 1904, pp. 260-261. 
Recent developments in gold dredging: Min. & Sci. Press, vol. 97, 1908, 
pp. 219-223. 
Gruetter, F. W. — Platinum on the Pacific Coast: Min. & Sci. Press, vol. 113, 1916, 

pp. 20-21. 
Halev, Charles S. — Dry placers of southern California: State Mineralogist's Rept. 
XVIII, 1922, pp. 321-324. 

Progress report on placer gold investigation : State Mineralogist's Rept. 
XVIII, 1922, pp. 373-374. 

Tertiary sluice robbers: State Mineralogist's Rept. XVIII, 1922, pp. 550-553. 
Gold placers of California: Cal. State Min. Bur., Bull. 92, 1923, 167 pp. 
including maps and charts. 

Primary and secondary gold concentrations : State Mineralogist's Rept. XIX, 
1923, pp. 38-40. 
Hall, C. L. — The gravel fields of Northern California: Min. & Sci. Press, vol. 74, 1897, 

p. 113. 
Hall, Frank H. — Ancient gravels, Siskiyou County, California : Min. & Sci. Press, vol. 66, 

1893, p. 85. 
Hammond, John Hays — The auriferous gravels of California: In H. C. Burchard 
Report of the U. S. Director of the Mint upon the statistics of the production of 
t'le precious metals in the United States for the Calendar Y'ear 1881, pp. 616-630 
(1882). 

Auriferous gravels of California ; geology of of their occurrence and methods 
of their exploitation; State Mineralogist's Rept. IX, 1888-1889, pp. 105-138. 
Hanks, H. G. — Placer, hydraulic, and drift mining: State Mineralogist's Rept. II, 1882, 
pp. 28-192. 

Placer Gold : In H. C. Burchard, Report of the U. S. Director of the Mint 
upon the statistics of the production of the precious metals in the United States 
for the Calendar Year 1882, pp. 728-732 (1883). 

Gold in river channels: Min. & Sci. Press, vol. 58, 1S89, p. 485. 

Deep gold placers of California : Min. & Sci. Press, vol. 60, 1890, pp. 231, 237, 

249, 255, 264, 271, 280, 296, 314, 315, 330, 331, 337, 347, 353, 361, 362, 378, 384. 

The deep-lying auriferous gravels and table mountains of California : San 

Francisco, 1901, 15 pp. 

Hanna, G. Dallas — Mammoth tusks found near Oroville, California: State IVIineralo- 

gist's Rept. XXV, 1929, pp. 88-90. 
Hay, Oliver P. — The geological age of the Tuolumne Table Mountain, California : Wash. 
Acad. Sci. Jour., vol. 16, 1926, pp. 358-361. 

The Pleistocene of the western region of North America and its vertebrated 
animals: Carnegie Inst. Wash., Publ. No. 322 B, 1927. 



212 PLACER MINING FOR GOLD. IN CALIFORNIA [Bull. 135 

JleilaiKl, (J. A., and Courtier, VV. H.- -Magiietometric investigations of gold placer 
deposits near Golden, Colorado : Am. Inst. M. & M. Kng., Geophysical Prospecting. 
1'J2'J, pp. :{04-3S4. (Notlilng on t:alifornia. ) 

Hershey, t ). H. — Neocine deposits of tlie Klamath region, California: Jour. tJeol., 
vol. 10, iyo2, pp. :iT7-:r.i2. . , .., . 

A supposed larly Tertiary peneplain in the Klanuith region, California: 
Science (n. s.), vol. 10, 1902, pp. la'J-lofi. 

The signiticance uf certain Cretaceous outliers in the Klamath ngion, Cali- 
fornia : Am. Jour. Sci. (4), vol. H. l'.io2, p. 33. 

The relation between certain river terraces and the glacial siries in north- 
western California: Jour. (Jeol., vol. 11, l'J03, pp. 4ai-4r>N. 

Certain river terraces of the Klamath river region, California: Anur. Jour. 
Sci. (4), vol. 10, l!)0:i, pp. 240-250. 

The river terraces of the Orleans Basin, California: Univ. Cal., Bull. Dept. 
Geol. Sci., vol. 3, l'J04, pp. 423-475. 
Hill, James M. — The mining districts of the western United States: Introduction by 
W. Lindgren: U. S. Geol. Survey, Bull. 507, 1'J12 (California), pp. 5-43. 

The l.os Burros di.-^trict, Monterey County, California : U. S. Geol. Survey, 
Bull. 735, 1923, pp. 323-329. 

California gold production, 1S49-1923 : Econ. Geol., vol. 21, 192G, pp. 172-179. 
Historical summary of gold, silver, copper, lead, and zinc products in California, 184S- 

1926: U. S. Bur. Min. Ec, Paper 3, 1929. 
Hinds, N. E. A. — Geologic formations of the Redding-Weaverville districts, Northern 
California: State Mineralogist's Kept. XXIX, 1933, pp. 114-122. 

Late Cenozoic history of southern Klamath Mountains: (Abstract) Pan. 
Am. Geol., vol. 51, 1934, pp. 315-316. 

Mesozoic and Cenozoic eruptive rocks of the .southern Klamath Mountains, 
California: Univ. Cal. Publ., Bull. Dept. Geol. Sci., vol. 23, 1935 (Tertiary), 
pp. 367-377. 
Hinds, N. E. A., and Russell, D. R. — lone formation of the Redding district: (Summary 

statement) Pan. Am. Geol., vol. 51, 1929, p. 375. 
Hitchcock, C. H. — The Calaveras skull: Eng. & Min. Jour., vol. 9, 1870, pp. 345-346. 
Hittell, John S. — The dead rivers of California: Overland Monthly, vol. 1, 1S6.S, pp. 
430-435. 

Dead rivers of California : In R. W. Raymond, Second Report on Mineral 
Resources of the States and Territories west of the Allssissippi, 1870, pp. 63-67. 
Hobson, J. B. — Placer County: State Mineralogist's Rept. X, 189U, pp. 410-434. 
Hoffman, Charles F. — The Red Point drift gravel mine : Trans. Tech. Soc. Pacific Coast, 

vol. 10, No. 12, San Franciscu. 1894, pp. 291-307. 
Holmes, W. H. — Review of the evidence relating to auriferous gravel man in California : 
Amer. Anthropologist (n. s), vol. 1, 1899, pp. 107-121, 614-645; Smiths. Inst. An. 
Rept., 1899, pp. 419-472 (1901). 
Holmes, W. H., and McGee, W. J. — Geology and archeology of the California gold belt: 

(Abstract) Am. Geol., vol. 23, 1899. pp. 96-99. 
Horner, R. R. — Notes on the black .sand deposits of southern Oregon and northern 

California: U. S. Bur. Min., Tech. I'aper 196, 191S. 
Hubbard, J. D. — Drift mining in California: Eng. & Min. Jour., vol. 104, 1917, pp. 

863-866. 
Hulin, Carlton D. — Geologic features of the drv placers of the northern Mojave Desert ; 

State Mineralogist's Ropt. XXX, 19:!4, pp. 417-426. 
Hurst, (;. L. — Re.soiling after dredging in California: Min. & Sci. Pre.ss, vol. 107, 1913, 

pp. 719-720. 
Hutchins, J. P. — The nomenclature of modern placer mining: Eng. & Min. Jour., vol. 84, 

1907, pp. 293-296. 
Irvine, C. D. — The beach placers of the south Pacific Coast: Min. World, vol. 29, 190S, 

pp. 321-322. 
Jackson, C. F., and Knaebel, J. B. — Small-scale placer mining methods: U. S. Bur. 

Mines, Inf. Cir. 6611, 1932. 
Jacobs, H. S. — Ancient river channels (California) : Min. & Sci. Press, vol. 34, 1877, 

p. 264. 
Jakosky, J. J. — Practical aspect of geophysical surveys: Min. Jour. (Ariz.), vol. 14, 
No. 16, 1931, pp. 7-8. 

Use of geophysics in gold mining: Min. Jour. (.\riz. ), vol. 15, no. 6, 1931, 
pp. 5-7. 37. 
Jakosky, J. J., and Wilson, C. H. — Use of geophysics in placer mining: Min. Jour. 
(Ariz.), vol. 16, No. 14. 1929, pp. 3-4. 

Geophysical studies in placer and water-supply problems: Am. Inst. M. & M. 
Eng., 'I'ecli. Publ. 51.'). 1934 (Trinity County placers), jip. 6-12. 
Jamison, C. E. — Santa (,'lara Placers: (Los Angeles and Ventura Counties). Min. 

& Sci. Press, vol. 100, 1910, pp. 360-361. 
Janin, Charles — I'resent day problems in California gold dredging: Min. & Sci. Press, 
vol. 103. 1911, pp. 474-478. 

Present day problems in California gold dredging: Trans., America Inst. 
Min. Eng., 42, 1912, pp. 855-873. 

Placer mining methods and operating costs: U. S. Bur. Min., Bull. 121, 1916, 
pp. 42-58. 

Topography and geology of dredging areas: Min. & Sci. Pre.ss, vol. 117. 1918. 
pp. 763-764. 

Gold dredging in the United States: U. S. Bur. Mines, Bull. 127, 191.S. 
Proposed regulation of gold-<lredging : Min. & Sol. Press, vol. 106, 1931, 
pp. 381-384. 
Janin, Charles, and Winston, W. B. — Gold dredging in California: Cal. State .Min. Bur. 

Bull. 57, 1910. 
Jenkins, Olaf P. — Report accompanying geologic map of northern Sierra Nevada : State 
Mineralogists Rept. XXVIII, 1932, pp. 279-298. 

Geologic map of northern Sierra Nevada showing Tertiary river channels 
and Mother Lode Belt: Cal. State Div. Mines, 1932; later reprinted, with modi- 
fications and report accompanying, printed un back of map. 



Se(;. II| (iKOLOGV OF I'LACKU I)K1-()SITS — .IKXKINS 213 

.IcnkiiiH, olaf P. (Cont.) 

I'se of KfoloKV in scekiriK pold : Min. Jour. (Ariz.), vol. 17, June 1^), l'J.,-i, p. ... 
.Middle California and Western Nevada: XVI Int. Geol. Congres.s, Guide- 
book 16. Ex. C-1, iri.'?.'',. 

Current note.s : (with notes on Beopli.vsical prospecting of buried river chan- 
nels by William U. Wright, Jr.), Stale Mineralr.^isfs Ilept. XXX, l!t:',4, pp. :{-4. 
U«'Surrection of earlv surfaces in the Sierra Nevada, a funrlamental geologic 
process involved in placer gold deposition: Cal. State .Mineralogist's liept. X.XX, 
in.34, pp. 5-r,. 

(ieologic map of .Mother I^ode Belt and vicinity d'J.'iL') : In State I)iv. .Mmes 
lUill. 108, by C. .\. Logan, IH.'U. 
Jenkins, Olaf I'., and AVrigbt, W. Quinby— California's gold-bearing Tertiary channels: 

Kng. & .Min. Jour., vol. 1 :!.'., lli:!}, pp. 4'J"-r)02. 
Kellogg, A. E. — Origin of flour gold in black sands: Min. .lour. (Ariz.), vol. U, no. 20, 

l!i;U, pp. :i-4. 
Kenii), J. F.--l'latinuiii and associat.nl m.tals : U. S. Ceol, Surv.y, Hull. UCi, lli02, 

l)p. ')1 -')'■',. 
Kimble, C.eorge W. — The Kimble Drift mine, El iJoradcj County, California: Min. & Sci. 
I're.ss, vol. .sr,, iiM)2, p. 2:i. 

Ancient river channels ~>f California: Min. & Sci. Press, vol. 94, I'.tO,, pp. 
726-727. 
Knopf, Adolph, The .Mother Lode systt-m of California : U. S. Ceol. Survey, Prof. Paper 
l.")7, i:)29. 

Tertiary auriferous gravels: .XVI Int. Geol. Congress, Guldel)ook ir,, Ex. C-1. 
I'J'.'i'i, pp. (JO-Gl. 
Knowlton, E. H. — Flora of the auriferous gravels of California: U. S. Geol. Survey, 

Prof. Paper 7:'., lUll, pp. .")7-.jS. 
Knox, N. 13. — Dredging and valuing dredging ground in Oroville, California : Canadian 

.Min. Pev., vol. 22, l!i03, pp. 211-213. 
Koch, Felix J. — The Calaveras .skull: Amer. Anticiuarian, vol. 33, 1911, pp. 199-202. 
Laizure, C. .McK. — lOlementarv placer mining methods and gold-saving devices: State 
Mineralogists liept. XXVIII, 1932, pp. 112-204. 

Elementary placer mining in California and notes on the milhng of gold 
ores: State .Mineralogist's Itept. XXX, 1934, pp. 121-2S9. 
Lakes, .Arthur — The deep leads of California: Colliery Eng., vol. 14, 1S94, p. 170; Mm. 
& Sci. Press, vol. 6.S, 1S94, p. ISf,. 

Fossilized big trees, California: Sci. .\m. Supl. 39, 1S95, p. 15862. 
Placer mining in (.California: Mines and .Minerals, vol. 19, 1899, pp. 297-29S. 
Gold bearing beach sands of California: .Mines and Minerals, vol. 19, 1899, 
p. 3(;9. 

Calaveras County mines (California) : Mines and Minerals, vol. 20, 1899, 
pp. 198-200. 
Lang, Herbert — Black sand of the Pacific Coast: Min. & Sci. Press, vol. 113, 1916, pp. 

Laur, P. — Terrains auriferes de la Californie : Rv. des deux mondes 33 annee (second 

period), 1863, pp. 453-472. ^ . 

Lawson, Andrew C— The geology of Middle California: XVI Int. Geol. Congress, Guide- 
book 16, Ex. C-1, 1933, pp. 10-12. 
Laylander, K. C. — Magnetometric surveying as an aid in exploring placer ground : 

Eng. & Min. Jour., vol. 121, 1926, pp. 325-328. 
Le Conte, Joseph — Post-Tertiarv elevation of the Sierra Nevada shown by the river 
beds: Am. Jour. Sci. (3), vol. 132, 1886, pp. 167-181. 

The old river beds of California: Am. Jour. Sci. (3), vol. 132, 1886, pp. 
176-190. 

On the origin of normal faults and of the structure of the Basm region : 
Am. Jour. Sci. (3), vol. 138, 1889, pp. 257-263. 

Critical periods in the history of the earth: Univ. Cal., Bull. Dept. Geol. Sci., 
vol. 1, 1895, pp. 213-336. 
Leidv, Joseph — Remarks on vertebrate fossils from Table Mountain, Tuolumne Co., 
■ Cal. : .Acad. Nat. Sci., Phila., Proc. 1870, pp. 125-227. 

Notes on Pleistocene mammals in California : In Whitney, J. D., "Auriferous 
gravels of the Sierra Nevada of California." Harvard Coll., Mus. Comp. Zool., 
Mem. 6, 1880, pp. 256-258; (another edition) Whitney, J. D., "Contributions to 
American Geology," vol. 1, 1880, pp. 256-258. 
Les(iuereux, Leo — Reports on the fossil plants, etc. : Mem. Mus. Comp. Zool. Harvard 
Coll., vol. 6, No. 2, Cambridge, 1878. 

The Cretaceous and Tertiary floras: Rept. U. S. Geol. Geog. Survey, Terr., 
( Havden), vol. 8, 1883. 
Lindgren, Waldemar — Two Neocene rivers of California: Bull. Geol. Soc. Am., vol 4, 
1893, pp. 257-298. 

An auriferous conglomerate of Jurassic age from the Sierra Nevada ; Amer. 
Jour. Sci. (3), vol. 48, 1894, pp. 275-280. 

Sacramento folio (No. 5) ; U. S. Geol. Survey, 1S94. 

The gold-quartz veins of Nevada City and Grass Valley districts, California : 
U. S. Geol. Survey, 17th Ann. Rept., Pt. 2, 1896, pp. 1-262. 
Nevada City folio (No. 29) : U. S. Geol. Survey, 1896. 
Pyramid Peak folio ( .Xo. 31) : U. S. (Jeol. Survey, 1896. 
Truckee folio (No. 39): U. S. Geol. Survey, 1897. 
Colfax folio (No. 66) : U. S. Geol. Survey, 1900. 

The gold production of North America, its geological derivation and probable 
future: Int. Min. Congress, 5th Proc, 1903, pp. 29-36. 

The geological features of the gold production of North America : Trans. 
Am. Inst. M. Eng., vol. 33, 1903, pp. 790-845, 1077-1083. 

Neocene rivers of the Sierra Nevada: U. S. Geol. Survey, Bull. 213, 1903, 
pp. 64-65. 

The Tertiary gravels of the Sierra Nevada of California: U. S. Geol. Survey, 
Prof. Paper 73, 1911. 



214 PLACKR MlNINfl FOR GOLD IN CALIFORNIA [Bull. 135 

Lindgron, Waldc-mar, and Knowlton, F. H.— Agre of the auriferous gravels of the Sierra 
Nevada, with a report on the flora of Independence Hill : Jour. Geol., vol. 4, 1896. 
pp. SSl-906. 
Lindgren, Waldemar, and Turner. H. W. — Placerville folio (No. 3) : U. S. Geol. Survey, 
1894. 

Marvsville folio (No. 17) : U. S. Geol. Survey, 1S95. 
Smart.sville folio (No. 18) : U. S. Geol. Survey. 1895. 

Reprints from Placerville, Sacramento, and Jackson folio.<! (Nos. .1. 5, 11) : 
U. S. Geol. Survey. 1914. 
Lindgren, Waldemar, and others — The production of gold and silver in 1904 : U. S. Geol. 

Survev. 100."); (California by Charles G. Yale. pp. 41-66). 
Locke A — Tuolumne Table Mountain (near Jamestown, California) : Min. & Sci. Press, 

vol. 105. 1912, p. 85. 
Logan, C. A. — Platinum and allied metals in California: Min. Bur., Bull. 85, 1919. 

Auburn field division : Amador, Nevada, Placer. El Dorado. Calaveras, Tuol- 
umne Counties: State Mineralogist's Rept. XIX, iy2;{, pp. i:!-21, 59-60, 94-97, 
140-145, 

Sacramento field division : Amador, Nevada, Plumas, Shasta, Sierra, Tuol- 
umne, M(ino, Placer, Sacramento, Yuba, Calaveras, El Dorado Counties: State 
Mineralogist's Rept. XX, 1924, pp. 1-23, 73-84. 177-1S3. 355-367. 

Sacramento field division ; Sacramento, Calaveras, Placer Siskiyou Coun- 
ties : State Mineralogist's Rept. XXI, 1025, pp. 1-22. 135-172, 275-280, 413-498. 
Ancient channels of Duncan Canyon region. Placer County, California: State 
Mineralogist's Rept. XXI, 1925, pp. 275-280. 

Sacramento field division; El Dorado County, California: State Mineralo- 
gist's Rept. XXII, 1926, pp. 397-452. 

Sacramento field division; Trinity, Shasta, El Dorado Counties: State Min- 
eralogist's Rept. XXII, 1926, pp. 1-67, 121-216. 313-452. 

Sacramento field division; Amador, Placer Counties. California: State 
Mineralogist's Rept. XXIII. 1927. pp. 131-202, 235-286. 373. 

Sacramento field division ; Tuolumne County, California : State Mineralo- 
gist's Rept. XXIV, 1928, pp. 3-53. 

Sacramento field division; Sierra County, California: State Mineralogist's 
Rept. XXV, 1929, pp. 151-212. 

Sacramento field division; Butte County, California: State Mineralogist's 
Rept. XXIV, 1928, pp. 191-210; XXVI, 1930, pp. 383-407. 

Sacramento field division; Nevada County, California: State Mineralogist's 
Rept. XXVI, 1930, pp. 90-137. 

Mother Lode gold belt of California: Cal. State Div. Mines, Bull. 108, 1934, 
including 6 geologic maps. 
Louderback, George D. — Morphologic features of the Basin Range displacements in the 
Great Basin: Univ. Cal., Bull. Dept. Geol. Sci., vol. 16, 1826. pp. 1-42. 

Notes on the geologic section near Columbia, California ; with special refer- 
ence to the occurrenee of fossils in the auriferous gravels ; Carnegie Inst. Wash., 
Publ. Paleo., vol. 440, 1934. p. 440. 
MacDonald. D. F. — The Weaverville-Trinity Centre gold gravels. Trinity County. 

California: U. S. Geol. Survey, Bull. 430, 1910, pp. 48-59. 
MacGinitie. Harry — Ecological aspects of the floras of the auriferous gravels: 
(Abstract) Bull. Geol. Soc. Am., Proc. 1, 1934, p. 356; (Abstract) Pan. Am. 
Geol., vol. 42, 1934, pp. 75-76. 
Maclaren, J. Malcolm — Gold : Its geological occurrence and geographical distribution : 

London, 1908 (California, pp. 503-514). 
Marcou, Jules — Sur le gisement de I'or en Californie: Arch. Sci. Phys. Nat, vol. 28, 
1855, pp. 124-135. Also in his Geology of North America, Zurich, 1858, pp. 81-84. 
Matthes, F. E. — Geologic history of the Yosemite Valley: U. S. Geol. Survey, Prof. 
Paper 160, 1930. 

Geography and geology of the Sierra Nevada: XVI Int. Geol. Congress, 
Guidebook 16, Ex. C-1, 1933, pp. 26-40. 

Up the western slope of the Sierra Nevada by way of the Yosemite Valley : 
XVI Int. Geol. Congress, Guidebook 16. Ex. C-1. 1933, pp. 67-81. 
Maxson, John H. — Economic geologv of portions of Del Norte and Si.skiyou Counties, 
Northwesternmnst California: State Mineralogist's Rept. XXIX. 1033, pp. 123-160. 
McGillivrav, J. J. — The old river beds of the Sierra Nevada of California: In H. C. 
Burchard, Report of the U. S. Director of the Mint upon the statistics of the 
production of the precious metals of the Ignited States for the Calendar Year 1881, 
pp. 630-644 (1882). 
Mendell, J. H. — Report upon a project to protect the navigable waters of California 
from the effects of hydraulic mining: In Repts. Chief Eng. U. S. Army; also 
House Ex. Doc. No. 98, 47th Cong., 1st sess., 1882. 
Merriam, John C, and Stock, Chester — Tertiary mammals from the auriferous gravels 
near Columbia, California: Carnegie Inst., Wash., Publ. Paleo., vol. 440, 1934. 
pp. 1-6. 
Miscellaneou.s — Statistical reports by the California State Mining Bureau, later called 
the Division of Mines. 

California Miners' Association Annuals. 
Mineral Industries, McGraw-Hill. 

Mineral Resources of the United States: U. S. Geol. Survey and later by 
U. S. Bureau of Mines. 

Debris Commission reports. 
Nason, F. L. — The Colder gold diggings: Eng. & Min. Jour, vol. 59. 1890, p. 223. 
Oldham, C. — Placer gold discovery in Greenhorn Gulch: Min. Jour. (Ariz.), vol. 15, 

no. 13. 1931, pp. 3-4. 
Pardee. .1. T. — Placer deposits of the western United States. In Ore deposits of the 
Western States: Am. Inst. M. & M. Eng. Publ., 1933, pp. 419-450. 

Beach placers on the Oregon Coast: U. S. CJeol. Survey, Cir. 8, 1934, 
pp. 4-41. 
Patmon, C. G. — Methods and costs of dredging auriferous gravels at Lancha Plana, 

Amador County, California: U. S. Bur. Min. Inf. Clr. 6659, 1932. 
Phillips, J. Arthur — A treatise on ore deposits: London, 2d edition, 1896 (California 
placers, pp. 19-27). 



Sec. 11] GEOLOGY OF PLACEK DEPOSITS — JENKINS 215 

Radford, G. K. — Mining for gold in the auriferous gravels of California: Inst. Min. 

Eng., Trans. 17, 1900, pp. 452-481. 
Ransome, F. L. — Some lava flows of the western slope of the Sierra Nevada, California : 

U. S. Geol. Survey, Bull. 89, 1898, 74 pp. 

Mother Lode district folio (No. 6;j) : U. S. Geol. Survey, 1900. 
Ransome, P. L., and Turner, H. W. — Sonora folio (No. 41) : U. S. Geol. Survey, 1897. 

Big Trees folio (No. 51) : U. S. Geol. Survey, 1898. 
Ravmond, Rossiter W. — Mineral resources of the States and Territories west of the 

Rocky Mountains: U. S. Treasury Dcpt., 1S69. 

Statistics of mines and mining in the States and Territories west of the 

Rocky Mountains: U. S. Treasury Dept., 1.S70-1S7G. 
Reid, J. A. — A Tertiary river channel near Carson City, Nevada: Min. & Sci. Press, 

vol. 9G, 1908, pp. 522-526. 
Rensch, H. E. & E. G., and Hoover, Mildred B. — Hi.storic spots in California: Stanford 

Press, 1933. 
Ricketts, A. H. — Manner of locating and holding mineral claims in California: Cal. 

State Div. Mines, Bull, 106, 1931 (Placer locations, pp. 9-10). 
Richards, R. H., and Dav, D. T. — Investigation of the black sands from placer mines: 

U. S. Geol. Survey, Bull. 285, 1906, pp. 150-164. 
Robinson, F. W. — Notes on hydraulic mining: State Mineralogist's Rept. II, 1882, pp. 

119-129. 
Robinson, L. L. — Impounding reservoir for mining and other debris. House Com- 
mittee on water rights and drainage, Assembly Bill 451, Feb. 17, 1887. 
Romanowitz, C. M., and Young, George J. — Gold dredging: Eng. & Min. Jour., vol. 135, 

1934. pp. 486-490. 
Rose, T. Kirke— The metallurgy of gold: 5th edition. London, 1906, pp. 45-92. 
Russell, Israel C.^Rivers of North America : New York, 1898 (California, pp. 275-278). 
Sampson, R. J.^ — Placers of southern California : State Mineralogist's Rept. XXVIII 

(Supplement), 1932, pp. 245-255. 
Sauvage, Ed. — De I'exploitation hydraulique de I'or en Calif ornie : An Mines (7), vol. 9, 

1876, pp. 1-77. 
Scupham. J. R. — The buried rivers of California as a source of gold : Mines and Min- 
erals, vol. 19, 1898, pp. 150-152. 
Shimmer, G. L. — Ancient river channels of California: Eng. & Min. Jour., vol.- 114, 1922, 

p. 857. 
Silliman, B. Jr. — On the deep placers of the South and Middle Yuba, Nevada County, 

California: Am. Jour. Sci. (2), vol. 40, lSfi5. pp. 1-19. 

On the existence of the mastodon in the deep-lying gold placers of Cali- 
fornia : Am. Jour. Sci. (2), vol. 45, 1S68, pp. 378-3X1. 

Notice of the peculiar mode of the occurrence of gold and silver in the foot- 
hills of the Sierra Nevada, and especially at Whiskey Hill, in Placer County, 

and Quail Hill, in Calaveras County, California: The Acad. Nat. Sci., Proc. 3, 

1867, pp. 349-351; Am. Jour. Sci. (2), vol. 45, 1869, pp. 92-95. 
Simpson, Edward C. — Geology- and mineral df-posits of the Elizabeth Lake quadrangle, 

California: State Mineralngi.«t's Rept. XXX, 1934, (placer deposits, p. 409). 
Sinclair, "V^^ J. — Recent investigation bearing on the question of the occurrence of 

Neocene man in the auriferous gravels of the Sierra Nevada: Cal. Univ. Publ. 

Am. Archaeology and Ethnologv, No. 7, 1908, pp. 107-131. 
Skidmore. W. A. — Deep placer mining in California : In R. W. Raymond. Third Report 

on Mineral Resources of the States and Territories west of the Mississippi, 1870, 

pp. 52-90 (1872). , , „. 

Hvdraulic mining at Gold Run — The Blue Lead ancient river channel : Mm. 

& Sci. Press, vol. 30, 1875, pp. 108-169. 

Gravel channels of ancient rivers: Min. & Sci. Press, vol. 51, 1885, p. 6. 
Smith, A. M., and Vanderburg, Wm. O. — Placer mining in Nevada: Univ. Nev., Bull., 

vol. 26, no. 8, 1932. 
Smith, J. P. — The geologic formations of California, with reconnaissance geologic maji : 

Cal. State Min. Bur.. Bull. 72, 1916. 
Smyth, H. L. — Origin and classification of placers: Eng. & Min. Jour., vol. 79, 1905, 

pp. 1045-1046, 1179-1180, 1228-1230. 
Sperry, E. A. — Investigation of Feather River black sands: Min. & Sci. Press, vol. 105, 

1912. pp. 624-626. 
Steffa, Don — Gold mining and milling methods and costs at the Vallecito Western Drift 

Mine, Angels Camp, California: U. S. Bur. Mines, Inf. Cir. 6612, 1932. 
Stewart, J. D. — Hvdraulic mining again interesting to capital: Eng. & Min. Jour., 

vol. 135, 1934; pp. 491-493. 
Storms, W. H. — Ancient channel system of Calaveras County: State Mineralogist's 

Rept. XII, 1894, pp. 4S2-492. 

Peculiar effect of subterranean corrosion of rocks (Tuolumne Co., Cal.) : 

Min. & Sci. Press, vol. 79, 1899, p. 5. 

Mother Lode region of California: Cal. State Min. Bur., Bull. 18, 1900. 
Ancient gravel channels of Calaveras County, California : Min. & Sci. Press. 

vol. 91, 1905, pp. 170-171, 192-193. 
Taylor, G. F. — The Brandy City hydraulic mine. Sierra County (California) : Eng. 

& Min. Jour., vol. S9, 1910, pp. 1152-1153. 
Theller, J. H. — Hydraulicking on Klamath River: Min. & Sci. Press, vol. lOS, 1914, 

pp. 523-526. 
Thurman, C. H. — Possibilities of dredging in the Oroville district, California: Min. 

& Sci. Press, vol. 118, 1919, pp. 257-258. 
Toleman, P. — Auriferous gravels of the counties : The Nevada City Nugget, Special 

Mining Number, May 10, 1929, pp. 19-21. 
Trask, John B. — Report of First State Geological Survey, Sacramento, 1853. 

Report on the geologv of the Coast Mountains and part of the Sierra Nevada : 

Calif. Assembly Doc. No. 9, Session of 1854. 

Report on the geology of northern and southern California : Calif. Assembly 

Doc. 14, Session of 1856. 



216 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 135 

Tucker, W. B. — Notes on mlnlnp activity In Inyo and Mono Counties In July, 1931: 
State MlneraloRlst's Rept. XXVII. 1931, pp. 543-546. 

South of the T^hM<>hapi i,'olil mitilnK makes new pain: Eng. &. Mln. Jour., 
vol. 135. 1935. pp. 517-521. 
Tucker, W. B., and Samp.<!on, R. J. — Los Anpeles Field Division; San Bernardino 
County : State Mineralogist's Rept. XXVI, 1930, pp. 221-260 ; XXVII, 1931 (Gold), 
pp. 2S0-333. 

Los Anceles Field Division; Ventura County (Gold): State Mineralogist's 
Rept. XXVIII, 1022, pp. 253-257. 

Gold rpsoiirces of Kern County, California : State Mineralogist's Rept. XXIX, 
1933, pp. 271-3.T0. 
Turner, H. W.— Mohawk lake beds: Bull. Wash. Phil, Soc, vol. 11, 1891, pp. 385-410. 
Jackson folio (No. 11) : IT. s. Geol. S\irvey, 1894. 

The rocks of the Sierra Nevada: U. S. Geol. Survey, 14th An. Rept., pt. 2, 
1894, pp. 441-495. 

Auriferous gravels of the Sierra Nevada: Am. Geol., vol. 15, 1895, pp. 
371-379. 

The age and succession of the igneous rocks of the Sierra Nevada: Jour. 
Geol.. vol. 3. 1S95. pp. 385-414. 

Further contributions to the geology of the Sierra Nevada: U. S. Geol. Sur- 
vey. 17th An. Report, pt. 1, 1X06, pp. 521-762. 

Bidwell Bar folio (No. 43) : U. S. Geol. Survey, 1898. 

The occurrence and origin of diamonds in California: Am. Geol., vol. 23, 1S99, 
pp. 182. 191. 

Post-Tertiary elevation of the Sierra Nevada: Bull. Geol. Soc. Am., vol. 13, 
1003, pp. 540-541. 

Cretaceous auriferous conglomerate of the Cottonwood Mining district, Sis- 
kiyou County. California: Eng. & Min. Jour., vol. 76. 190."?, pp. 653-654. 
Turner. H. W.. and Ransome, F. L. — Sonora folio (No. 41) : U. S. Geol. Survey, 1897. 

Big Trees folio (No. 51) : U. S. Geol. Survey. 1808. 
von Bernewitz. M. W. — Dredging and resoiling: Min. & Sci. Press, vol. lis, 1919, p. 471. 
Weatherbee, D'Arcy — A hydraulic mine in California: Min. & Sci. Press, vol. 93, 1906, 
pp. 296-208. 

Dredging and horticulture: Min. & Sci. Press, vol. 94, 1907, p. 151. 
Whitney, J. D. — Geological Survey of California, Geology: vol. 1, Philadelphia, 1S65. 
Notice of a human skull recentlv taken from a shaft near Angels, Calaveras 
County, California: Calif. Acad. Nat. Sci.. Proc. 3. 1867. pp. 277-278. 

Sur les amas detrlliciue de la Californie : Soc. Geol., France, Bull. (2) 24, 
1S67, pp. 624-625. 

The auriferous gravels of the Sierra Nevada: Mem. Mus. Comp. Zool. Har- 
vard Coll., vol. 6, 1879, p. 659. Includes chapters by W. A. Goodyear and W. H. 
Pettee. 

The climatic changes of later geological times: Mem. Mus. Comp. Zool. Har- 
vard Coll.. vol. 7. pt. 2. 18S4. p. 394. 
Wiel, S. C. — The ancient channel of Gibsonville, California : Mln. & Sci. Press, vol. 91, 

1905. p. 73. 
Williams, Howel — Geology of the Afarysville Buttes, California: Univ. Cal. Dept. Geol. 

Sci. Bull., vol. 18. 1929, pp. 103-220. 
Wilson, C. H. — Economic value of geophvsics in mining: Min. Jour. (Ariz.), vol. 15, 

no. 21, 1032, pp. 3-5. 
Winslow, C. F. — On human rcinains along with those of Mastodon in the drift of Cali- 
fornia : Boston Soc. Nat. His., Proc. 6, 1S57. pp. 278-270. 
Wright. G. F. — The lava beds of California and Idaho, and their relation to the 
antiquity of man: (Abstract) British Asso. Rept. 61. 1892, p. 651. 

Evidence of Glacial man in America: (Abstract) Amer. (Jeol., vol. 12, 1S93, 
pp. 173-174. 

Recent volcanic eruption in California : Amer. Nat., vol. 27, 1803, pp. 813-816. 
Recent date of lava flows in California: Records of the Past, vol. 4, 1005, 
pp. 19.5-198. 

The latest concerning pre-historic man in California: Records of the Past, 
vol. 7, 1908. pp. 183-187. 
Yale, C. G. — Auriferous gravel — a theory of its formation : In H. C. Burchard, Report 
of the U. S. Director of the Mint upon the statistics of the production of the 
precious metals in the United States for the Calendar Year 1880, pp. 376-379 
(1881). 

Mining debris legislation: Cal. Mines Assoc, Mines and Minerals, 1889, 
pp. 255-262. 

Beach mining in California: U. S. Geol. Survey, Min. Res. for 1912, pp. 253- 
254 (1913). 

Dry placers of California: U. S. Geol. Survey, Min. Res., pt. 1, 1913, pp. 
262-263. 
Yeatman. J. A. — The pump in placer mining: Min. & Sci. Pres-s, vol. 88, 1904, p. 226. 
Young, George J. — California's gold dredge in operation over twenty years : Eng. & Min. 
Jour., vol. 121, 1927, pp. 1042-1046. 

Drift mining at Vallecito, Calaveras County, California: Eng. & Min. Jour., 
vol. 128. 1929. pp. 394-307. 
Zadarh, Stanley — Placer mining in San Gabriel Canyon: Min. Journ. (Ariz.), vol. 17, 
no. 3, 1933, p. 3. 



SECTION III 



PROSPECTING AND SAMPLING PLACER DEPOSITS 



SAMPLING 

Nothing: is more important to the success of a placer mine than to 
determine in advance that the gravel in question contains enough gold 
and possibly metals of the platinum group, to return a profit. Money 
received for the metals sold must be sufficient to pay for the cost of 
operation plus the cost of all equipment plus royalties or cost of land 
plus interest on the investment plus a reasonable profit. Of course, if 
the equipment is to be used on more than one deposit, amortization of 
its cost may be distributed accordingly. A large proportion of all placer 
operations has failed because the gold in the gravel was insufficient to 
repay the cost of even the most efficient mining, not to mention the 
return of monej* invested or interest thereon. 

Many methods of sampling are available, including the simple 
panning of gravel from natural exposures, drifting, test-pitting or 
trenching, shaft-sinking, and churn-drilling. Actual mining on a small 
scale often is done as a method of sampling prior to investing considerable 
money in development or equipment. Panning, rocking, and small-scale 
machines have been described in Section I, under Small-Scale Methods. 
All of these are useful in prospecting and sampling. Small machines 
driven by gasoline engines have been much used in recent sampling jobs 
to save labor. 

Weight of Placer Gravel 

Placer gravels vary greatly in weight per cubic yard in place and 
percentage increase in volume on being loosened. Yet in making esti- 
mates of yardage and value it often is necessary to use some factor to 
convert volume in place into loose volume or into tonnage. In common 
placer terminology "heavy" gravel indicates coarse rather than weighty 
material. The weight is greater in tight or cemented than in loose ground, 
and it increases with the proportion of large boulders and heavy rock 
material such as diorite, greenstone, or hornblende schist. The amount 
of moisture present likewise affects the weight. 

Three contiguous samples taken by Gardner and Johnson ^ from 
the same bed of tight, fine clayey gravel overlying a pay streak in the 
Greaterville district, Arizona, indicated weights of 3,450 pounds, 3,540 
pounds, and 3,000 pounds to the cubic yard, respectively, or an average 
of 3,300 pounds. A sample of clean gravel with 30 to 40 percent cobbles 
over 2J inches in diameter, from another gulch in the same district, 
weighed 3,600 pounds to the cubic yard in place. The samples contained 
5 to 8 percent of moisture. The expansion of the first three samples was 
50, 54, and 33 percent, respectively, an average of 46 percent. The last 
.sample expanded 17 percent. 

The gold-bearing river gravel at the pit of the Grant Rock-Service 
Company, Fresno, California, weighs 2,850 pounds per cubic yard. Some 
engineers in calculating tonnage allow 3,000 pounds to the cubic yard, 
bank measure. Handbooks give weights per cubic yard ranging from 
2,600 to 3,650 pounds. An average weight probably is between 3,000 
and 3,300 pounds to the cubic yard. 

' Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, 
Part 1, General information, hand-shoveling, and ground-sluicing: U.S. Bur. Mines. Inf. 
Circ. 6786, p. 27, 1934. 

(219) 



220 I'LACKU MINING FOK GOLD IN CALirOKNIA [Bull. 135 

Sampling Natural Exposures 

Whonevor a ^'old pan is used skillfully tlio result not only proves or 
disjjroves the preseju'e of i;old but also usually shows aeeurately the 
amount of prold contained iu the sample ehosen. l'annin<r along a creek 
bed thus is the most elementarj' method of sampling a placer deposit. 
However, the samjiles commoidy are taken so as to render the quantita- 
tive results worthless. 

A gravel deposit of much size seldom can be sampled directly from 
its natural exposures; but a few creek banks, steep-sided gulches, or old 
excavations such as hydraulic pits may be available, in which case certain 
precautions should be taken to get true samples. F'irst, the vertical 
extent of gravel to include in a given sample should be determined. If 
hydraulicking is to be done, the whole depth of gravel ordinarily is 
included in one sami)le, except when it is planned to pijie off the barren 
overburden to waste, in which event it is desirable to know the depth of 
barren material and samples may bo taken of each distinguishable 
stratum. If drifting is planned, only the lower, economically minable 
gravel need be sampled. After the location and extent of a sample cut 
have been decided, care must be taken to have equal (juantities of gravel 
from all points along its length. The best way to do this is to cut a chan- 
nel or groove of uniform shape and size from top to bottom of the sample 
distance. Enough such samples must be taken to prove the continuity of 
the "pay streak." 

Mechanically the ]>rocedure of sampling a gravel face resembles 
closely that pursued in lode mines. A pan and a pick are the requisite 
tools. The bank should be trimmed well and cleaned ahuig the sample 
line to eliminate effects of surface weathering. The pan may be used 
to catch the loosened material, or a canvas may be spread on the ground. 
If conditions favor it, a measurable channel or groove should be cut so 
that the volume taken can be measured. Otherwise, the only alternatives 
are to use a factor for pans per cubic yard or to measure the loose gravel 
in a box which has been calibrated in terms of bank measure. 

Drifting 

Drifting is a common method of prospecting a deep placer deposit 
when coiulitions are favorable. The cost of driving a small drift in 
placer gravel ordinarily ranges from $2 to $(j per foot. Diflfieult ground 
conditions or excessive water may increase the cost to $10 or $15 per foot. 

For sampling purposes the gravel usually is taken to the surface 
and concentrated in sluice boxes. If an old drift is being sampled various 
methods may be followed. If the ground will permit, the most .satis- 
factory method is to slab 1 or 2 feet from the side of the drift and wash 
the gravel thus broken. If not, vertical channels may be cut on one or 
both sides of the drift at intervals of about 5 feet. If the latter is done, 
the volume of the sample cut may be mea-sured, which is preferable under 
most conditions, or a factor may be used for reducing loose measures 
of gravel to solid measure, which facilitates taking the sample but intro- 
duces some uncertainty and leads to carelesness in sampling. If values 
are to be expressed in cents per ton it is still necessary to decide what 
conversion factor to use in making estimates of tonnage. 



Sec. Ill] SAMPLING 221 

Test-Pitting 

Test-pittiiif? and ti-t'neliiiiL>- nrc fii)i)lii-al)lp only to ^i-avels so .sliallow 
that a man can throw out the dii't by hand. Tlie best procedure is to 
mark out the area of the pit on the surface, makinjr it rectangular, as 
small as convenient, and jireferably in dimensions of even feet such as 2 
feet wide and 3 or 4 feet huig. Then it shouhl be excavated to bedrock 
with smootli, vertical walls. Sometimes a cleared space is prepared and 
the dirt thrown on the bare ground, but in view of the greater difficulty 
and possible small error involved in rehandling the dirt it is better to 
shovel it onto a canvas or board platform or into a receptacle. If a large 
boulder projects iiito the pit no correction of the theoretical volume of 
gravel should be made, regardless of whether or not the bo\dder is 
removed oi- allowed to remain in place, as obviously it can not be ignored 
in mining operatituis and is the equivalent of so much barren gravel. 
The gravel taken from the pit may be thrown into one or more piles, 
depending on whether or not information is desired regarding one or 
more individual strata. Sometimes alternate third, fourth, or tenth 
shovelfuls are used for the .sample to reduce the volume to be panned or 
otherwise concentrated. This should be avoided whenever practical 
because of the possible error introduced. 

The cost of sinking test pits or running trenches in earth and gravel 
has been noted often enough for fair generalizations to l)e established. 
Gardner - states that opencast work in placer ground costs from $0.40 
to $1 per cubic yard, depending on the nature of the ground and on 
wages. AVages for such work then ranged from $3 to $4 per 8 hours. 
Furthermore, a nuni should be able to pick and shovel about 8 cubic 
yards of fairly loose gravel in 8 hours. \n test pits the worker's efficiency 
would be lowered somewhat by the cramped quarters and by the care 
necessary to square out the corners and trim the sides to vertical planes. 

The spacing of test pits depends on the nature of the deposit. If 
the pay gravel occurs in narrow channels the best plan is to space the 
pits in lines across the channels, as is done with churn-drill holes when 
sampling dredge ground. The holes must be close enough to yield an 
average value which represents the average value of the channel at 
that point. In practice the spacing ranges from a few to 50 or 75 feet, 
depending on the uniformity of results. The transverse lines of pits 
theoretically should be placed close enough to show either fairly uniform 
values from line to line or a rea.sonable upward or downward trend of 
gold content along the channel, rnfortunately, this is seldom po.ssible, 
and the usual practice of spacing the lines from 100 to several hundred 
feet apart is a compromise in the engineer's mind between the cost of 
sampling and the need for accurate results. 

Shaft-Sinking 
Shaft-sinking is a connnon method of testing placer ground. Pros- 
pect and sampling shafts, unless intended for later use in drifting or 
mining and unless exceptionally deep (75 feet or more), are sunk as 
small as practicable. The u.sual section is rectangular and 3 by 4 to 4 by 6 
feet in size. Kound timber 4 to 6 inches in diameter, which is available 
in most districts, is commonly used to crib shafts in loose gravel. In 
gravel tight enough to stand safely without lagging the only timber 

- (jardner, E. D., Cost of mine opening.'; : Eng. and Min. Jour., vol. 100, pp. 791-794, 
Nov. 13, iyi5. 



222 PLACKR MINING FOR GOLD IN CALIFORNIA [Bull, 135 

necessary is .stalls sot to liold the ladder. A hand windlass is the usual 
means of hoistinjr, usiiijjf a lif^ht steel, 2-cu.ft. bucket and a f- or 1-inch- 
dianieter nianila rope, as ordinary wire rope is unsuitable for a windlass; 
75 to 100 feet is the niaxiinuni depth at which such e(iuipnient can be 
used most efiiciently. For j^reater depths a power hoist of some kind 
should be installed. Lar<re boulders can be lifted with the ordinary 
hand windlass if it is provided with long cranks; as nnicli as 800 pounds 
can be raised by two men. Such feats, however, are considered danjzerous 
because of the jreneral absence of safe brakes or catches on windlasses, 
and the possibility of killinj,' or injuring the operator if he loses control 
of tlie ci-ank handle. 

All of the {gravel removed from such a sliaft is often trucked to a 
stationary washing plant to recover the gold. The gravel is dumped 
into a hopper from which it is fed to a revolving screen or trommel 
equipped with a water-spray, and undersize is washed in sluices. If 
these are placed in steps, so that the gravel drops from one to the next 
below, the necessity for tight cross-joints is avoided. Slopes of the boxes 
can be adjusted to give good recoveries for different types of gravel. 
In one actual case 4 boxes were used, each 10 feet long, 10 inches wide, 
and H inches deep. Grade of the fii'.st three boxes was set at 1^ inches 
per foot, and of the fourth at -i-inch per foot. In shafts that stand 
without timber, the gravel may be sampled by cutting a vertical channel. 
A common size is 1 foot wide and 1 foot deep. Care should be taken 
with bedrock, which should be removed for at least a few inches in depth, 
and then brushed clean. Ilecovered gold should be weighed on an 
accurate balance, and an occasional assay should be made to determine 
the fineness of the gold. 

Where gravel is loose, sometimes steel tubes about 4^ feet in diameter, 
called caissons, are sunk as the shaft is excavated, to hold the walls. 
An example of this method in which telescoping caissons were used is 
given in the table at the end of this section. If the shafts are wet, and 
pumps driven by engines or motors are needed, this method becomes 
very expensive, and drilling may be used instead; although drilling is 
a less accurate method of sampling. 

Drilling 

Placer deposits, particularly those being considered for dredging, 
are often sampled by drilling, which could be called drive-pipe sampling 
with more accuracy. The casing, usually a G-iiu'h pipe with a special 
shoe, is driven a foot at a time into virgin gravel, then the core of grav?l 
that rises in relation to this pipe is cut by the bit of the churn-drill and 
bailed out with a sand pump. Water is added to all holes. The cut- 
tings from each foot are panned by an expert panner, and the weight of 
the gold in each i)an is estinuited. The colors of gold from the pans 
from a single hole ai"e combiiunl and amalganuited with a drop of quick- 
silver. This gold is later recovered fi-om the amalgam by the engineer 
and actually weighed. 

The drill in common use is the Keystone, made by Keystone Driller 
Company, Heaver Falls, Pennsylvania. Califoi-nia agents arc Ilarron, 
Rickard and McCone Company, 2070 Bryant Street, San Francisco, or 
3850 Santa Fe Avenue, Los Angeles. Late designs include model 70 
mounted on a truck, and model 71 on crawler tracks. According to the 



Sec. Ill] SAMPLING 223 

manufacturer, model 71 will climb grades of 50 percent when loaded witli 
necessary tools and equipment. 

The object of this type of drilling is not to make rapid progress with 
the hole but to get accurate samples. Drilling would proceed at a much 
greater speed if the bit of the churn-drill were kept ahead of the casing, 
but this is never done in sampling unless a boulder must be broken to 
allow driving of the casing, because the volume of gravel removed from 
the hole would not be known. When the casing is driven a foot at a time, 
volume may be calculated as that of a cylinder a foot long and with 
diameter equal to the outside diameter of the cutting slioe, usually 7^ 
inches. "Water is added to dry holes so that tlie cuttings may be with- 
drawn by means of a suction sand-pump. Water is added to wet holes 
to keep the water-level in the hole higher than the natural ground-water 
level. This helps to prevent excess material from entering the casing. 
When bedrock is reached, the casing can no longer be driven, but drilling 
is continued for a few feet to recover gold on bedrock and to make sure 
that the casing is not resting on a boulder. Sometimes the drill strikes 
a fissure in bedrock and an abnormal amount of gold is recovered. In 
such a case the panner should keep this gold separate from gold recovered 
from the gravel, and hand it to the engineer as a separate button of 
amalgam. 

The engineer dissolves the mercury from the amalgam with nitric 
acid of specific gravity 1.42 diluted with an equal volume of distilled 
water, washes the gold well with boiling water, then dries and anneals 
the gold in a small porcelain cup. Sometimes a little alcohol is added 
to the wash-water to prevent sputtering when drying. The dried gold 
dust is weighed on a balance sensitive to a milligram or less. Fineness 
of the gold must be determined by an occasional fire-assay. If platinum 
is present, concentrates from panning must be saved and weighed, 
then sent for chemical analysis. The amount of gold in cents per cubic 
yard for the gravel removed from the hole is calculated as follows : 
W X M X 27 

~" Dx 0.3068 
in which V rvalue of the gravel in cents per cubic yard 

W = weight of gold recovered from the hole in milligrams 
M = price in cents of a milligram of gold 
27 = number of cu. ft. in 1 cu. yd. 
D=depth of hole in feet 
0.3068 = area in square feet of shoe-circle 71 inches in diameter. 

The value of M depends on the price of gold and its fineness. When 

gold is $35.00 per ounce and the gold recovered is 900/1000 fine, it is 

calculated as follows : 

-, 3.^00 X .9 ... 

^ oTin'^ — = 1^1 cents per milligram. 

When a long narrow deposit is being sampled, such as bars along a 
river, rows of holes are often drilled acrass the bars at distances of 1000 
feet along the river. Holes in the rows are often about 150 feet apart. 
Whenever erratic occurence of gold in the bars is found, the spacing 
should be changed to suit local conditions. WTien the spacing of holes 
is irregular, the average value per cubic yard of the whole bar is found 
by weighting the value found in each hole by the area represented. The 
area between adjacent holes is multiplied by the average value in cents 



224 



PLAOKR MINIXG FOR GOLD IN CALIFORNIA 



[Bull. 135 



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-.-ill 



il liii|i 



1 



s. I 



m n 



~ -j' O !0 O 






s - 



ous; 



SSc 



!--^2 8 



c E 



If IliiJ 






gSS8 






gggsfg 



• « ■« TT O C M 

1 — » — O <c m 

• (N M — o d — 

. X U5 •» 3C "»■ g 









s s 



s § 



o>o>oc 

<oeMCM'< 



gggg — >OiO 

oc to C4 US 1^ r-^ 



:g';2gsr!gs 



Ss 



uso tx.So u. 






III 



52 



. Ill I ti=i^l'^'^"^Bzmi = « 
^IIJ-^I -^ I' 



o 

sir 






Sec. Til] SAMPLING 225 

per cubic yard for tlie two holes. This is continued across the line of 
lioles and the two columns of fifjures representing: areas and areas timas 
cents per cubic yard are added. Total of the last column divided by total 
area j^ives the avera<ie value per cubic yard of the line of holes. Allow- 
ance nuiy be nuule for small areas to be worked beyond the last holes 
at either end of the row. If the gold value of the holes is decreasing 
rapidly toward the ends of the row, this small area will be assigned a 
suitable fraction of the value per cubic yard of the last hole in the row. 
Allowance must be made for rising bedrock at the point where the bottom 
of the dredge would strike it; also for a foot of barren badrock to be 
excavated by the dredge. 

For the constant 0.3068 in the denominator of the above formula, 
some engineers have substituted the quantity 0.27, because the sampling 
done by drills usually gives a figure that is too low for the value per 
cubic yard of the gravel. Other engineers wish to discount their results, 
and substitute 0.8333 for 0.3068. Such substitution is bad practice 
because it causes confusion. If the engineer feels that his figures should 
be increased or decreased for any reason, he should state the reason and 
the percentage of increase or decrease. In all cases he should report the 
actual number of milligrams of gold recovered from the hole. 

A log-sheet for such a drilling job contains 11 columns, and an 
entry is made in each column every time the casing is driven a foot. 
Column no. 1 is an entry of the total depth to which casing has been driven 
in feet and tenths of a foot ; column no. 2 is the length of core after 
driving (length of casing minus length of tools and cable below top of 
casing with tools resting on top of core) ; column no. 3 is length of core 
in casing after drilling (about 0.3 feet) ; column no. 4 is length of core 
after pumping ; column no. 5 is actual depth of hole to top of core ; 
column no. 6 is an estimate of the number of milligrams of gold and is 
divided into three sub-columns; (a) milligrams of gold in particles over 
7 milligrams in weight, (b) milligrams of gold in particles 2 milligrams 
to 7 milligrams in weight, (c) milligrams of gold in particles less than 
2 milligrams in weight; column no. 7 is an estimate of amount of gravel 
caught in pan expressed in units of 'panfulls' (normally 0.75) ; column 
no. 8 is time of day at which pumping was finished ; column no. 9 is a 
description of the firmness of the gravel (loose, firm, or very firm) ; 
column no. 10 is type of material (soil, clay, cemented gravel, fine gravel, 
medium gravel, coarse gravel, or large boulders) ; column no. 11 is 
remarks (occurrence of some unusual mineral, rusty gold, change in 
character of gold, causes of delays, or anything else important or 
unusual). 

Gardner and Johnson ^ have published a table of drilling results 
compared with actual recovery by dredging on 40 different tracts of land. 
On 23 of the tracts recovery w^as more than 100 percent of the gold con- 
tent indicated by the drill-sampling, on 16 tracts recovery was less than 
100 percent, and on one tract, recovery was practically 100 percent. 
When recovery is less than 100 percent, the dredge may have left some 
of the gold behind. This is practically unavoidable where bedrock is 
very hard, and contains cracks and fissures into which the gold can settle 
beyond reach. No satisfactory method has yet been devised for accu- 
rately calculating percentage recovery by a dredge. However, when 

3 Op. cit, pp. 42-45. 
15 



22C) i'i.A( i:i{ Aii.\i.\<; iok <:n\.\) i\ ( Ar.iioKNrA [liiill. l;).") 

i-fcovcry is iiinrc tliaii 1(»U percfiil, it can iiicaii only tliat saiiipliii^- rt'siilts 
wore !(»(» low. 'i'lic majority ol" oases iiiciil ioii(><l above fall iiilo lliis class. 
Shafts that have been sunk arouiul drill holes have indicated the same 
tiling; recovery of fiold ])ei- cnhic >ard from the shaft has been ;:i-eater 
than that from the drill-hole. 

]{es\d1s of drill-saiiiplinji- are likely to be low in loose <;ravel snch as 
tailin^r, because of poor eoi'e-recovei-y. Drivinjr the casin}J: will push 
some of the ^i-avel aside, and tlie bit of the drill will |)ush moi-e of it. 
aside. The sand-pinnp is used as much as possible after the casinj^- is 
driven and befoi-e drilling' is started. However, some of the •ri'Mvej is 
usually too lai'Lic 1o pick up with tlie i)uni|). and the bit must be iiseil to 
break it up. 

Table 1 and the following' (piotation ai'(^ reproduced from \' . S. 
]>nreau of .Mines Information Circular ()7S() by (larduer ami .lohnsou."* 

••'I'lic iiri.s|ic(l iii;r was carried to a conclusion in i-;ich iiistnncc. I)n-(l;;in^' ful- 
lowrd I 111- inDsin'ciin;; in f<inr fif the .six cases. 

••'I'lir l.ir;;.' .iitlVirncr in c.st <ii cnuinrcrin;; li.-lwern .i..l.s n<>. 1 and no. -J was 
<lnr lo liic nmcli lar^.-r ovcrln'ad at n<>. L' on account of tin- nature of tlie (leposil. Tiie 

distance from liead.jnarters at S.ui Francisco also .•ilTecied tin- size of the en«;i rin^ 

fon-e necess.-ii'.v <ni the ^ronnil. .Jo!) no. '.', was in effect two jolis. Tile w..rl< was 
inleirnpted for a full year. 

'Mol, no. 4 was favored l.y :in .•iniple force of experience.! ;;ra\<'l miners, .-i |..w 
w.iter le\el. and no! a dilli.ull (inantity to liandle. 1 >iapliraf;ni hi\iH' pumps wen- used 
:ind in some siiafls In., d.-ep for sucti.m. a s.'coiid sliaft sunl< 10 f.-et d.'<"p and a.ljacenr 
to tiie first was used for increasing; the effective deptii, i.y means of two lifts. 

'•.Foil no. ."( was a very diflicult undertaUiiiK ••nid required llie use of steel tele- 
scoping' caissons, esiiecially di'si<;ned for the joh. (Jasolini'-driven pumps of the jack- 
iie.id deep-well cylinder ty|>e proved vi'ry awkward liut most effective. 

••In liotli .i<.l.s no. 4 and no. .". the total contents of the sli:ifts were washed in a 
lon^-tom device hy hand and in jol. no. 4 a check samiile was cut from (he side of the 
shaft and washed in a rocker. 

"Joli no. I> is a typical c:ise of shaft prosiiectiiis in frozen ground when- the ^'ravel 
deposit is unusually thin or shallow. Here (he conditions for shaft work were very 
favorable, hut (he hi;;h cos( of li\ in^' was reflected in (ho unit cost. Where experienced 
men are available, as in this case. ;ind ecpiipnn-nt developed by the miners for inacces- 
sible places is at hand f>>i- tln-ir use. a very low unit cos( is obtained. 

"Drilliii};: in fro/.en ground is also very economical, owinu to the sjieed w iiii which 
the work is accomplislie<l .-md the absence of casing' costs. The volume of sample is 
(piickly ami accurately obtained Ity water measurement after completion of the hole. 

"The unit cost or cost per foot for placi-r pros|iectin^' is usually uncertain, since 
il depends upon the total foota;ie. The nuinlier of holes or cross sections as the case 
reipiires may prove to be very few, and the total cost of slartin;; and clearing up the 
job falls uiion a small total foota^r'. Two c.ises can be cited as follows: One in 
Colombia, S. A., cost about $L'."),000 for about 1 ,r)00 feet of drilling where the equipment 
was left behind and never salvaged. Another in c<'nlral Alaska cost about the' same for 
less than .".(M) feet of drilling where the e(iuipment was not .salvaged on account of cost. 
In such cases and in many olhers that constandy arise costs can be reduced to a very 
low lifjiire by a preliminary e.\aniina(ion made by an experienced and reliable placer- 
mining engineer and are usually repre.sen(ed by (he engineer's fee and expenses. The 
number and distribudon of i)rospec( holes needed to piovide (he essential information 
<-an bo readily determined by the i)re|imin.ir.\ survey." 

1 Op. (it., p. ::.-.. 



GEOPHYSICAL PROSPECTING 

Geophysical inetliods liavo been used to a limited extent for tracing 
buried river channels containing' gravel (lei)osits. Such methods must 
be used iu connection with a caixd'ul study of the local geolopy ; other- 
wise interj^retation of the i-esults will be impossible. (ie()i)hysical 
methods may <>ive infoi-mation about the coui'se and the depth of the 
channel, but they tell noth.in^- whatever about the jiold-content of the 
gravel. This must be detei-miued by one of the sampling methods 
described above. 

Magnetic methods may be used where the gravel has either a higher 
or a lower magnetic ])ermeability than the underlying bedrock. How- 
ever, if a lava capping exists over the gravel magnetic conditions in 
this may interfere so much that the method cannot be applied. If the 
gravel contains concentrations of magnetite-sand, a magnetic survey 
will reveal magnetic 'highs'. On the other hand, if the bedrock is more 
magnetic than the gravel, the channel may be outlined by observing the 
magnetic 'lows' above it. Ellsworth^ describes such a survey made 
of a channel, of which the position had already been determined by 
mine-workings, at Forest Hill Divide, California. The instrument used 
was the Hotchkiss Superdip magnetometer. 

The U. S. Bureau of Mines was developing a method of tracing 
buried river cliannels by resistivity measurements before the war. This 
method shows promise of considerable success, but those in charge of 
the work have not yet been able to put the results in report-form 
because of the search for strategic minerals after the war started. 

A channel located in California has been outlined by a large 
geophysical engineering company with seismic work by the refraction 
method. The results were later confirmed in part by drilling. Although 
officials of the company which did this work feel that the method 
possesses merit, they do not want to report on it because results obtained 
by them have not yet been checked by actual mining. 

Some results of geophysical surveys at the Koseoe Placer of 
Humphreys Gold Corporation in Colorado have been described by 
Dart Wantland.- Both resistivity and magnetic methods were used. 



1 Ellsworth, E. \V., Tracing: buried river channel depo.sit.s by geomagnetic method.s : 
California .lour. Mines and (Jeology. vol. 2H, pp. 244-250, 1933. 

- Wantland, Dart, A coinparisoii of geophysical surveys and the results of opera- 
tions at the Ro.scoe Placer of the Humphreys Cold Corporation, Jefferson Cnmity, 
Coloradcj : Colorado School of Mines Quart., vol. .'^2, no. 1 , January 1 9:57. 



(227) 



SECTION IV 



PLACER MINES BY COUNTIES 



111 the following' pages are listed ]n-operties which have been 
operated recently, or which tire tlioiigiit to contain reserves of placer- 
gravel. They are to be regarded as examples only; more complete lists 
will be found in reports on individual counties contained in onr Cali- 
fornia Journal of ]\Iines and Geology. 

The California State Division of Mines does not sample placer 
mines. This involves a campaign of drilling or one of the other methods 
described herein in Section 111, Prospecihuj and Scnnpling Placer 
Deposits, and the Division of Mines is not equipped to do this work. 
Any statements contained liei-ein regarding the amount of gold in placer 
gravels have been obtained from j^crsons not connected with the Division 
of Mines, but oidy figures that are believed to be reliable have been used. 
Readers should not invest m(>n(\A- in e(|nip])ing or purchasing placer 
mines on the basis of these figures. The value of deposits should be 
checked by a competent engineer using the methods described in Section 
III before an investment is made. 

Figures on the production of certain operations are given below. 
Such statistics are collected by the W S. l^ureau of Klines ami have been 
compiled by Merrill.^ 

All but a few of California's gold mines were shut down late in 
19-^2 by Limitation Order Ti-2()8 of the AVar Production Board, which 
remained in effect until Julv 1, 1045. 



1 Merrill, C. \V., and Gaylord, H. ]M., Clold, silver, cii)i)er, lead, and zinc in California 
(Mine Report) : U. S. Bur. Mine.s Mineral.s Vearlxioks, 1;M0 to 1U4.;. 



( I'-XJ ) 



L»:{() 



ri,.\(i:i.' .\ii\i\<; I'ok- cdi.i. i\ ( Ai.iioHMA [r.iill.]:{5 




Sec. IV] MINKS T5Y COUNTIES 231 

AMADOR COUNTY 

All< n Rdncli. Iloiiry and AVcavor operated a drajrline dred<,'e on 
llie Allen Kancli })r()i)erty on Sutter Creek (iuleh during part of 1041. 
The (lra«iline exeavat(»r Avas equipped Avitli a ^-(Mil)ic yard bucket. 

.{)n<idor Drcdghu/ (U))np(ii}y, Tone, operated a dragline dredge in 
tlie lone district during 1941. 

Arroyo Scco Gold Drcdf/irif/ Compainf, .'{51 California Street, San 
Fi-ancisco, operated an ele('tri(; connected-bufket dredge, eipiipped with 
eighty-six 6-cu.ft. buckets from January 1 to May 1"), ]94]. The 
company ojiei-ated throughout 1040 also at a property 3 miles west 
of [one. 

J)(fcrt I'Jslafr. Mountain Gold Drcdt/ing Conipauy of Plymouth 
and AV. 1). Ingram operated dragline dredges on this property near 
J*lymouth during 1941. 

Ingram ojierated also on Indian Creek 4 miles west of Plymouth 
with two dragline excavators equipped with 25-cu.yd. and l-cu.yd. 
Inickets. Land was restored for agricultural use by leveling tailing and 
i'e]ilacing overburden. 

Elephant Hydraulic Mine. This mine, near Volcano, was operated 
in 1932 by the K. D. Winship estate. One and one-half to 3 feet of 
gravel on decomposed slate bedrock are overlain by 40 to 4.3 feet of 
volcanic ash. AVater amounting to 13.') miner's inches was delivered to 
one no. 2 giant through 18-inch and 8-inch pipe-lines under 11.") feet 
of head. CJold was recovered in a sluice 18 inches wide, 16 inches deep 
and 32 feet long, erpiipped with Hungarian riffles. Two men whose 
wages were .'f^3..")0 per 9-hour shift washed 3G00 cubic yards during a 
90-day season at a total cost of .$0.20 ])er cubic yard for labor and supplies. 
The volcanic ash was drilled with hand augers, blasted and piped through 
the sluice. Cravel was tight but was cut by the giant. Bywash-water 
amounting to 40 miner's inches raised the total through the sluice to 
17.1 inches. 

Garibaldi Mine. Caribaldi Bros., of Volcano operated a nonfloating 
washing plant, to which gravel was delivered by mechanical means, at 
their mine on Pioneer Creek half a mile east of Volcano, intermittently 
during 1941. The yield from 33.200 cubic yards of gravel was 229 
ounces of gold and 3.") ounces of silver. This mine was worked during 
parts of 1940 also. Garibaldi or Boardman property was operated by 
dragline and dry-land dredging in 1942. The dragline dredge recovered 
775 ounces of gold and 102 ounces of silver from 172,200 cubic yards of 
gravel, and the drA'-land dredge recovered 157 ounces of gold and 23 
ounces of silver from 35,500 cubic yards of gravel. 

Horfieshoe Dredginy Company, Tone, operated a dragline dredge in 
the lone district from May 2 until July 26, 1940. 

Horton Mine. This mine is in Jackson Valley 5 miles south of Tone 
and was operated by H. C4. Kreth of Tone by hydraulicking from January 
to June and from October to December, 1941. 

Independenee Gold Mi7ies. This company treated 12,100 cubic yards 
of gravel in the Camanche district at a stationary wa.shing plant between 
July 30 and October 12, 1941, recovering 187 ounces of gold and 19 ounces 
of silver. 



232 I'LACKK MINING I(»K COLO IN (Ar.IFORMA [Bull.l3o 

Irish Hill Minr. :\rcQuP('n and I)o\viiiii<r, 1040 :^^tll Street. Sacra- 
iiionto, ojicrated a drajrliiio dredge at tliis mine from March 28 to June 
2r,J041. 

Kent Proinrhi. Diiriiifr 1040. E. A. Kent, ^7)1 California Street, 
San Francisco, opei'atcd two drajrline di'('d<i:e.s on Sutter Creek between 
the towns of Sutter Creek and Volcano. One was equipped with a l:",- 
eu.yd. bucket, the other with a 2!-cu.yd. bucket. 

Lanchd Plana (ioUl J)r((h/i)i(/ Compaiij/, La Lomita liancho, Locke- 
ford, operated an (decti'ic connected-bucket dredjic, eciuipped with sixty- 
five 42-cu.ft. buck(>ts on Jackson Creek near I'uena \'ista throu<;hout 
lf)40 Jind from January 1 to .May \. 1!I41. wlicn it was di.smantled and 
moved to l^.utte Count\'. 

Jjorcntz Propcrhi. Lurcnl/ and Swiniile and Loinj liar Gold Dndfj- 
iiu/ (^ompanji operated dra'^line drcdu'es on this propci'ty on tlie Cosum- 
nes Kiv(M- in 1!*42. 'J'hc company i-ecovered 1140 ounces of <roKl and 13S 
ounces of silver from 200.000 cnbic \ards of ^i-avel. Lorentz and Swinp;le 
also operated on Cosumncs Kivei-. 7 miles luirthwest of Plymouth in 1941. 

Mainlich Prt/jx rhi. Moinitnin dohl Drrdf/infi Cdinixinn of Plym- 
outh operated a di-a^line di-cdnc at this pi-ojierty neai- Diytown inter- 
mittently durin<r lf)41. 

Mcdulloh Prujx rhi. I'ncijic Placers Engiticcriiuj f'onipanji, 3400 H 
Street, Sacramento, operated a drapline dred<re on this property in the 
lone district durinjr jjarts of 1!)40 and 1941. Yield from 350,000 cubic 
yar<ls of <.rravel was 274f) ounces of <rold and 258 ounces of silver in 1!)41. 

Pension Mine. Lone/ liar Gold Drcdr/inf} Conipanjf, 935 Forum 
IJuildiufr, Sacramento, operated a draj^line dredj>e at this mine from Sep- 
tember 13 to 28, 1942. A volume of 14,000 cubic yards of <rravel yielded 
87 ounces of gold and 12 ounces of silver. 

Placrritas Mini)i<j (^onijxinn, 245 North (ii-ainercy Place, Lo.s 
Anjreles, operated a di-agline di-edjre on six ditferent properties in 1940, 
all within a radius of 4 miles from T*lymouth. 

Rim Cam Gold J)r( (h/inf/ Ctunpinni operated a (li-a<rline di-edj:e on two 
l)ropei-ties near T)i-yto\vn and on the Cosunnies Kiver between Plymouth 
and Xashville in 1!>40. (See also Ya<nr Ranch.) 

River Pine Mining Comjxinn. This company, address of which was 
Plymouth, opei-ated a drajiline di-edge near Aukum, whieh was equipped 
with a l''-cu.yd. bucket, from January 1 to June 12, 1941, when, it was 
moved to El Doi-ado County. The yield from 300,000 cubic yards of 
^i-avel was 1380 ouiu*es of jrold a)ul 192 ounces of silvei- in 1941. This 
was the most productive drajrline dredjre in the county in 1940. 

Rupleif Ranch. This property is on Willow Creek 5 miles w^est of 
Drytown. J. (•. Pantle operated a dry-land dredfje here from January 
1 to October 15, 1942. He recovered 1290 ounces of jrold and 183 ounces 
of silver fi-om 230,000 cnbic yai'ds of jrravel. A (lraj>line 'excavator 
ef|uipped with a l.l-cu.yd. bucket (hdivered {Travel to the washinji: i)lant. 
Tlie yield in 1941 was 1850 ounces of jrold and 254 ounces of silver from 
:;(i(),000 cubic yards of prravel. In 1940. Pantle 's recovery from 205,000 
cubic yards of <;ravel was 1154 ouiu-es of trold and 139 ounces of silver. 

San Andreas Gold Dredf/inf/ Company, 960 Russ Building, San 
Francisco, operated a dragline dredge with H-cu.yd. bucket on the 
Arroyo Seco Ranch during part of 1940. 



Sec. IV] MINES BY COUNTIES 233 

Treble Clef Mine. E. L. Lilly, 706 California Building, Stockton, 
operated a dragline dredge with 21-cn.yd. bucket during parts of 1941. 
The outfit Avas operated throughout lf)40 on two different properties. 

Yiujcr lidnrh. Rim Cam Gold Dycdf/iitfi Compan]) operated a drag- 
line dredge on tliis propei-tv in the Tone disti-iet from February 4 to 
May 26, 1941. 

BUTTE COUNTY 

A number of drift mines in Butte County such as the Ennna, Indian 
Sjirings, and Perschbaker were ver}- productive years ago, but drift 
mining has not been active in the county recently. Segments of the 
iniderground channels renmin un worked, but prospecting, development- 
work, and sampling are needed to determine whether they can be worked 
at a profit. Further details are given by Logan^ and Lindgren.^ Recent 
l)r()duL'ti()n of the county has been mostly from dredging. The principal 
producers of placer gold from 1940 to 1943 are mentioned below. 

Amo mine in Oroville district was operated in 1942 by F. C. Peter- 
son, Box 550, Oroville, who used a non-floating washing plant and 
recovered 379 ounces of gold and 12 ounces of silver from 60,000 cubic 
yards of gravel. 

Baker and McCowan, Palermo, operated a dragline dredge on the 
Farnan Ranch in the Oroville district in 1940. 

Butte Operatinrj Company, Oroville, operated a dragline dredge in 
the Oroville district throughout 1940. 

Conj and Strong Placer is 2.8 miles by road north of Stirling City 
and contains 320 acres in the Ei .sec. 16, t! 24 X., R. 4 E., M. D., on the 
west side of West Branch of Feather River. A large lava-covered 
trough, locally known as the Mammoth Channel, crosses the property. 
Bedrock rims are 1500 to 2000 feet apart. Years ago, an adit was driven 
at a point 400 feet south of the north property-line to a length of 700 
feet. It is in lava-wash supposed to be higher than the main channel 
but George E. Strong of Dixon, California, states that it produced 
enough gold to pay for the work. 

Strong says that a shaft, which was kept nn watered by a 3-inch 
pump was sunk on the bank of the river, and that a drill-hole was put 
down 454 feet from the bottom of the shaft in sand and clay to reach 
hard bedrock. He is planning some more drilling in an effort to locate 
gravel containing gold in paying amounts. 

Gold Hill Dredging Company, 311 California Street, San Fran- 
cisco, operated a connected-bucket dredge with seventj^-four 9-cu.ft. 
buckets on the Wilton Kister propertv, on the east side of Feather 
River 7 miles south of Oroville during 1940, 1941, 1942. 

Golden Feather Dredging Company, 817 25th Street, Sacramento, 
operated a dragline dredge, using a 5-cu.yd. bucket, on the Feather 
River opposite the town of Oroville from February 1940 until late in 
1944. This operation was given a special permit by the War Production 

1 Log-an, C. A., Butte County: California Div. Mines, Mining in California, State 
Mineralogisf.s Rept. 26, pp. 383-40G, 1930. ^ ^„. 

Logan, r. A., Butte-Countv : California Jour. Mines and Geology, vol. 31, p. 6, 193.T. 

2 Lindgren, W"aldemar, The Tertiarv gravel.s of the Sierra Nevada of California: 
U. S. Geol. Survey Prof. Paper 73, pp. S4-&3, 1911. 



234 I'LAfiiR :\ii\ix(; for com) in cAr.ii'ORXiA [ I'.iill. l:!.") 

H(tar(l hpcaiisc jri-avel was clt^arod from tlic Fcathor TJivcr cliaiiiu'l and 
stacked a.s a Icvoo to protect tlie town of Orovillo. Furtlier details liavc 
boon puhlisbod by Wiltsee."' 

Unin})hrciifi Gold Corporation, 010 First National Rank P>uildin«r, 
Denver, Colorado, operated a dry-land drod<re on tlie T.. T. Ivister i)rop- 
erty, Oroville district, duriiifr part of 1040. 

Jiitrrstnfr ^fincfi, Inc., Ohieo, moved a di-a^line drcdjrc from 'I'l-init.v 
Conntv to tlie Cianella "Ranch. Oj-oville district, and operated it during 
part of 1040 and 1041. 

Knufuhl (171(1 T)(ni{so)i, Oroville, worked tbe Foi-d ])i-operty dnrinj,' 
part of 1041. The excavator used a 1-eu.yd. bucket. 

Lnvchn Pinna Cold Drrdfjiiu/ Company, La Tiomita Rancho, Tioeke- 
ford, moved its eonnected-bneket dredge from Amadoi" County to the 
l>utte Creek district, resumed operations iu October 1041, and worked 
until October 12, 1042. The dred<«e had .sixty-five 4^cu.ft. buckets. 

T.cmroh Mininrj Company, 2401 Bayshore Boulevard, San Fran- 
ci.sco. operated a drajrline dredire in the ^Nfajralia district durinji' i)art of 
1040. In 1041, this company operated a dragline dredtre u.sin<r a 2^cu.- 
yd. bucket; 504,848 cubic yards of g:ravel yielded 2730 ounces of ^old 
and lOo ounces of silver. 

Lord and Bishop (Lohicasa Company after January 1. 1041 ). Box 
812. Sacramento, washed 66,300 cubic yards of jrravel by dra^iiine 
dredjiiji<r in the Oroville district durinpr part of 1040 and recovei-ed 336 
ounces of ^'old and 11 "ounces of silver. The dragline excavator had a 1 .]- 
cu.vd. bucket. Tn 1041, Lobicasa Company operated on the Peters 
Ranch. 

Morris Ravine Mining Company, Oroville, dperated a drift mine in 
the Oroville district in 1042 and recovered 6r)8 ounces of ^old and 65 
ounces of .silver from 850 cubic yards of gravel. This mine was worked 
in 1043 also. 

Oroville Cold Dredging Company, 2052 Bird Street, Oroville, 
operated a connected-bucket dredge with seventy-two 8.1-eu.ft. buckets 
on the Ilazelbusch and T. !^^. Rogers tracts on Featlier Rivei- miles 
southwest of Oroville during 1041 and part of 1043. 

Piedmont Dredging Company operated a Becker-IIopkins type 
dredge on Butte Creek during part of 1041. Recovery from 20,502 
cid)ic yards of gravel was 121 ounces of gold aiul 10 ounces of silver. 

Piomho Bros, tf; Company, 1517 Turk Street, San Francisco, oper- 
ated a dragline dredge, using a l.^-cu.vd. bucket, on French Creek 
throughout 1040 and 1041. 

Placer Development Company, 2401 Bayshore Boulevard. San 
Francisco, operated a dragline dredge in the Oroville district during 
l>art of 1040, and at Meadows 3 miles south of Oroville in 1041. The 
dragline excavator used a bucket of 2i-cubic yards. 

Placer Exploration Company, Box 408, Chico, operated two drag- 
line di-edges in the Oroville district in 1041. One was equipped with 
a 5-«Md>ic yard bucket, the other with a 2J-cubic yard bucket. Several 
l)roperties were worked including the following: Dagorret, California 
Tjands, Inc., and Innis. In 1041, this company worked on the Gianella 

• Wlltsee, E. A., Operations of Golden Feather Dredging Company: Min. Cong. 
Jour., pp. 21-24, 35, August 1944. 



Sec. IV] MINES HY COUNTIES 235 

Ranch;- also dnrinp: part of 1942. The Tunis Ranch was worked in 
1942 also. 

William Richfer tO So^is, Oroville, operated a dra<?line dredge on 
the Douglas Jacob, Mary ITarrin, V. Gamble, and John Bilkli prop- 
erties in the Oroville district in 1940. They worked on the following 
properties in Oroville district in 1941 : Belkriet, Bilkli. Freidel, Helen 
Whittier, Hume and Coleman, John Aim, Lorrie, Ray Angle, Rottinger, 
and Wyandotte. 

Su7imar Dredging Company, Box 228," Oroville, operated a drag- 
line dredge in Weymans Ravine 4 miles from Oroville during part of 
1940. The dragline excavator used a 2-cubic yard bucket. In 1941 this 
company used e(iuipment with IJ-cubic yard bucket on the following 
properties : Clark, Cratt, Schwartz, Crowder and Binney, Darby, Darby 
ynd Crowder, Leal, and Schwartz and Pedrazzini properties. This 
company worked on the Gianella and Peter properties in 1942. 

Yiiha Consolidated Gold Fields, 351 California Street, San Fran- 
cisco, operated four electric connected-bucket dredges in the Oroville 
district during the 4-year period under consideration until October 15, 
1942. Bucket-lines were as folloM's: eighty-four 9-cubic foot buckets, 
eighty-nine 9-cubic foot buckets, eighty-seven 9-cubic foot buckets, and 
seventy-one 6-cubic foot buckets. 

CALAVERAS COUNTY 

The drift mines of Calaveras County are of outstanding interest 
although all other types of placer mines have been operated in the 
county, and dredges have been very productive. For further informa- 
tion on .such operations the reader is referred to State Mineralogist's 
Report XXXII ^, which contains descriptions of many mines and a long 
table of references to descriptions of older operations. Maps showing 
the ancient channel system at Mokelumne Hill, San Andreas, Angels 
Camp, and Vallecito are included in this report, and are sold separately 
by the Division of Mines. Considerable detailed information on these 
channels is contained in Bulletin 413 of the U. S. Bureau of Mines.^ 
Descriptions of the Vallecito-Western and Calaveras Central mines are 
reprinted herein because they show recent trends in the mechanization 
of drift mines. The need for extensive preliminary work to prepare 
such a mine for the production of a large tonnage per day is clearly 
indicated. The principal channels in this county are at a lower eleva- 
tion than the present surface and are reached by shafts. 

Calaveras Central Mine 

The Calaveras Central ^ mine is of especial interest because it is the 
largest drift mine in California, and its management has pioneered in 
the application of more recent and more effective engineering methods 
to produce large tonnage at low cost. The results so far achieved, with 

1 Logan, C. A., and Franke, H., Mines and mineral resources of Calaveras County : 
California Jour. Mines and Geology, vol. 32, pp. 324-364, 1936. 

2 Julihn, C. E., and Horton, F. W., Mineral industries survey of the United States; 
California, Calaveras County, Mother Lode District (south). Mines of the Southern 
Mother Lode Region, Part I, Calaveras County: U. S. Bur. Mines Bull. 413, pp. 21-94, 
1938. 

» Julihn, C. E. and Horton, F. W^, op. cit. 



236 I'LACKR MINIXC. VOK COLD IN' CAMFORNIA [BuU. 135 

imicli yet n'lnaiiiiii^' to Ix- done in the (Icvelopinent of improved prac- 
tice, at least jioiiit tlie way toward the only course likely to revitalize 
drift niinin<r. wliich lias so lon^r been moribund. Tbey demonstrate that 
reasonably lar^e, steady production attained thro\i<rh increased mechani- 
zation, similar to that already in use in many lode mines, is highly effec- 
tive in reduciufr the costs of drift mininpr as well. 

The mine is about 1 mile north of An<,'els Camp, it is ojjcrated 
by the Calaveras Central (Jold :\Iinin«jr Co.. Ltd., TOo llobart Jiuild- 
in<r, San Francisco. The data in re<:ard to these ojierations were 
made available for .study by Harry Sears, i^resident and ^^Mieral man- 
ajrer, from records of his company. 

The company is said to control, by ]on<r-tci-iii leases, 870 coiitijxiious 
acres, extendin<r about .'U miles aloufr the Central Hill Channel of the 
main Tertiary Calaveras River, in sees. 21, 22, 23, 2(), 27, and 2S, T. 3 X., 
]{. 13 E. This includes mining ri-rhts in areas foi-nuM-ly controlled by 
the Victor, McElroy, Pierano, and Reiner mines, the E. W. .lohnson ranch, 
the Slab Ranch, and other mines (»f the Calmo Minin<i- & Miliin<r Co. 

History and Production 

The first recorded development on this ])roperty occui-red before 
18()6. when the McElroy shaft was sunk on an intervolcanic channel 
called by the same name. This shaft, ])erhaps one of the first in Cali- 
fornia to be sunk in an attempt to mine deep gravels by svu'h means, was 
about 200 feet deep. It was equipped with a hoist operated by a primi- 
tive overshot water wheel. It penetrated rich jrravel, but after about 
$100,000 had been produced from a short distance along- the chainiel, 
operations were stopped by floodin<r. 

About 1866 the Mattison shaft was jiartly sunk on T.ald Hill, the 
site of the present hoist and com])i-essor buildings, and in the bottom 
pravels of that shaft the much publicized Calavei-as skull, that ])roved 
to be a hoax, was alleged to have been found. Other desultory attempts 
to reach and work the gravels of the area continued but accomi^lished 
little, and production amounted to only about 2000 ounces of gold from 
1000 to June 1031, when the present company began operations from a 
previously existing three-compartment shaft 3r)0 feet deep. Since then 
it is said to have produced 20,000 oinices of gold, bringing the total 
production during the present century to 22,000 ounces. 

The Gravels and Channels 

The Tertiary system of gravels is well -re presented by the' various 
chaiuiels within the boundaries of the property, ranging from a system 
of at least three prevolcanic channels in the bedrock to later super- 
imposed intervolcanic channels, and so up to recent gravels, which ai-e 
present at many places on the surface. Most of these surface gravels 
contain a little gold, and the richer ones were worked in early years. 
They have, of course, no relation to the deep jiay gravels of the ancient 
channels, which are buried beneath 250 to 350 feet of rhyolitic and 
andesitic tuffs, intercalated with beds of gravel, all of which are said to 
carry some gold. 

Just east of Slab Ranch the bedrock rims outlining the Tertiary 
valley in which the ancient river flowed are less than 500 feet apart, 
but the valley widens rapidly downstream, and a mile below this narrow 
neck it is more than one-half mile wide and forms a considerable basin. 



Sec. IV] MINES BY COUNTIES 237 

At Slab Ranch the old river flowed due west, but on entering the basin 
it coursed northwesterly and in turning cut several distinct channels 
separated by bedrock ridges or islands. Three bedrock channels in 
the basin have already been partly explored, but there is at least one 
other channel that lies somewhere in the deeper ground to the northeast 
that has not yet been reached. The southwest or Aetna Channel is 
unquestionably the yoinigest of the three, as it has cut through both the 
otliers. Similarly, Central Hill Channel, on which the main shaft is 
situated, is younger than No. 5 Channel, which it has cut through both 
to the southeast and northwest. Although the local relationships of these 
three channels are known, more exploratory work must be done, par- 
ticularly on the channels to the east, before they can be definitely cor- 
related with each other and with the main channel of the ancient river. 
There is evidence that Aetna Channel is not one of the main-stream 
channels but that it entered the basin through a gap in the rimrock to 
the south. Its gravels differ considerably from those in the other 
channels and contain a greater proportion of quartz sand and boulders. 
Its gold is relatively small and for the most part little worn, numerous 
pieces with quartz matrix adhering to them indicating that the gold has 
not traveled far from its source. On the contrary, in Central Hill 
Channel the gold is large and well worn. Nuggets weighing 1 penny- 
weight to 1 or 2 ounces occur frequently and the gold is identical in 
character with that from the Vallecito-Western and Golden River mines 
upstream. There is little question, therefore, that this channel was 
formed by the Tertiary Calaveras River, but there is evidence that it 
may not have been its original or main channel. In No. 5 Channel the 
gold is medium coarse and flaky and there are very few large nuggets. 
Further, the gravel in this channel is relatively shallow and the over- 
lying rhyolite tuff in some places reaches the bedrock on the benches, 
practically all of the gravel having been swept away. In most of these 
cases, however, enough gold was left in the creviced bedrock to make it 
worth mining. In the Aetna and Central Hill Channels the gravel is 
very thick, and nowhere have the workings reached the overlying vol- 
canic ash. In one instance the gravel of the Central Hill Channel 
overlaps a thin layer of volcanic ash, which caps No. .5 Channel. This 
not only confirms the greater age of No. 5 Channel but suggests that the 
undiscovered channel in the deeper ground to the northeast may have 
been the original channel of the main river through this basin. If this 
is true, it has an important economic bearing, as it is reasonable to suppose 
that the original channel contains the richest concentration of gold. 

Superimposed above this system of bedrock channels in the basin 
are intervolcanic channels in rhyolite, of which little is known and of 
which only the McElroy has ever been worked. This channel lies above 
the lowest stratum of rhyolitic tuff and enters the basin from the south 
along the eastern edge of the Mother Lode. Presumably it derived much 
of its gold from the erosion of quartz veins and stringers of the Mother 
Lode formation, which passes through the southwestern end of the 
property. This section is near such famous mines as the Utica, Lightner, 
Angels Quartz, and Sultana, and numerous quartz stringers have been 
cut in running bedrock drifts, which invariably have shown values in 
gold ; in one instance a 4-foot vein found in the Aetna w^orkings yielded 
a cut sample which assayed 0.20 ounce of gold. 



238 I'LAfKIJ MINING I'OU (\()\A) IN ( AI,! FOHN lA [Ullll.!^.") 

Xo iiiollcii liivjis iiiviulcd this hiisiii, l)iit tlicrc were two distinct 
periods ill which heavy bhmkets of rhyolitic tntV.s were laid (h)Wii, aiul 
a third and later jx-i-iod during- which sexeral liundred i'eet of andesitic 
tuffs were deposited. In some ])laees the andesitic tuff.s have been eoin- 
))letely or nearly lemoM'd hy erosion, while in otheivs 100 feet or more 
of them still remain. 

The Calaveras Centi-al shaft j)asses through the followin;^: .secpience 
of sti-ata: To feet of andesitic tuff, M.l feet of brown jiravel, !)() feet of 
rhyolitic tiilf, 20 feet of <;ray o;i-avel, 15 feet of rhyolitic tiitl", and GO feet 
of bluish <ii-ay <:ravel, which is more oi- les.s cemented by calcium car- 
bonate. Normally, the lower 'i or 4 feet of <>ravel within the confines (jf 
the channels comprises the richer i)ay. The vertical limits of the pay 
yi-avel, however, vary widely, and in one place on Xo. 5 Channel ^ood 
jxrouud was mined for 21 feet above bedrock. This is an exceptional 
instance and in most cases only the lower 4 to 6 feet of jiravel and 1 to :{ 
feet of the bedrock are mined. The width of the i)ay j;ravel varies 
^M-eatly. In No. 5 Channel it is 50 to 70 feet and in Central Hill and 
Aetna Channels 150 to 200 feet. The bedrock throujihout the workin-zs 
i.s either Calaveras slate or schist. The orijiiual grade of the bedrock 
channels has been altered by a gradual uplift of the country towai-d the 
northwest, ])robabIy caused by faulting movements. A gradual eleva- 
tion of the bedrock downstream has resulted. 

The gravel itself is composed lai'gely of well-rounded porphyiy, 
granite, gi-anodiorite, and considerable (puirtz. ]\Iany large boulders 
are found. The gold is coai-se, most of it being retained on a 10-mesli 
screen, and it is about HH~) fine, the imi)urity being lai-gelx- silvci'. It is 
associated with considerable jjyi'ite and a little black sand. 

Development 

Whei'i the proi)erty was taken over by the i)resent comijany there 
were three shafts on the tract. The thi'ee-compartment HeiiuM- shaft 
is ;i50 feet deep; the Aetna shaft, about !)()() feet southea.st of it, is 
240 feet deep; the McP]lroy shaft, about 1200 feet southwest of the 
Kciner shaft, is 200 feet deep. The Reiner shaft was reconditioned 
to bee(mie the main Calaveras Central working shaft, the Aetna shaft 
being retimbered and connected undei-ground with the maiu work- 
ings so that it affords the emergency exit required by California law 
and assists materially in ventilating the mine. Although the McElroy 
shaft was sunk about 80 years ago, it has not caved aiul may later be 
retimbei-cd and used in working the McElroy channel. Connecting it 
with the present workings would aid greatly in their ventilation. The 
position of these .shafts with relation to the underground woi-kings and 
the channels that have been developed so far are shown in figiiies l:{ 
and 14. 

The (irst work done by the present com])any, slai'ting in 1!»:{1, was 
to rnii a cros.scut from the station of the main shaft 800 feet nortli- 
easl, with the object of reaching the original channel, which lies in 
this direction; but 520 feet from the .shaft No. 5 Channel was inter- 
.sected, carrying excellent values in fine and medium-coarse gold. 
Hecaiise of the lu'cessity of i)r()ducing j)i()m])tly, most of the develop- 
ing and mining done iluring the next 2 years was confined to this 
channel, which was explored for IGOO feet upstream, where it was 
cut off by a deci)er channel, apparently the one on which the main shaft 



St'i. I\'J MINKS BY (;oi;xTiF,s 239 

is situated. iv\rcll<'iii pay gravel was roiiiul in this (U'cpt'r j,a'()Uiid, 
hut IK) hi-castin;^ was doiii', as new, h)W-levt'l, hedrock haida<iP tunnels 
must be driven before this ai-ea can be mined economieally. 

From ]"J34 to ]!);}(>, inelusive, most mining' and development were 
oil the Central Hill Channel, which was followed downstream 2700 
feet from the shaft. About ].')()() feet from the shaft this channel was 
( nt throu<.ih by the Aetna Channel, the discovery of which at this 
intersection lias assisted materially in establishing- its position and 
bedrock j^rade and ])roves that it can be i-cached by crosscuts to the 
southwest from the workings on the Central Hill Channel, thus opening 
it for mining at many ditiferent places and ovei- a considerable distance. 
Development has been confined to the three channels mentioned, which 
have been opened for a ma.ximum length of over 4000 feet ; but, owing 
to the large number of cross(;uts and parallel drifts, total development 
ai)i)roximates 3(),()00 feet. The total length of the three channels opened 
is estimated in a recent report to comprise only about one-tenth of the 
entire length (»f channels in the property, and only a small part of the 
gravel in the developed portion has been mined, with the previously 
stated yield of 2(),()()() ounces of gold. 

The company has not yet started operations on the area obtained 
trom tiie Calmo ^Mining & Milling Co., later called ]Mound City Gold 
.Mines, Inc., but two shafts were sunk previously. One of them, the 
Slab kancli shaft, was sunk in a narrow gorge where the rimrocks 
were only about 500 feet apart at the surface. The negative results 
should have been foreseen, as retention of gold there should not have 
been expected. 

The original Calmo shaft was sunk farther downstream near the 
north rim, and a small amount of gold, valued at about $25,000, was 
produced. It included a nugget weigliing 20 ounces, but this gold 
came from rim gravels, as the main channel appears to lie farther 
south in deeper ground not reached as yet. 

The plans of the present company contemplate exploration of that 
area by proceeding upstream on the channels that may be followed 
from present workings in the normal course of operations. The main 
cro.sscut is to be extended to the northeast until it encounters the main 
channel, which has not been reached as yet. This channel likewise will 
be sought at a higher level by a crosscut from the southeast end of 
the pi-esent workings. The Aetna Channel Avill also be crosscut in 
several places and opened for mining, a number of existing drifts being 
connected to serve partly develoi)ed sections of the mine. 

Reserves and Values of Gravel 

A recent report estimates that in pi-esent workings there are 328,000 
tons of high-grade gravel, averaging $5.32 a ton, and 117,000 tons of 
low-grade gravel, averaging $1.19 a ton, shown by present develop- 
ment work. These values are based upon past recovery from adjacent 
gravels. It can be increased in future operations b}' reducing the 
tailings losses, which have been excessive. The low-grade gravel is 
so situated that it can be mined by drag scraping at little cost, which 
is expected to permit some profit. These reserves, claimed as now 
assured, represent but a small part of the total length of the channels 
in the property. ]\IucR of the unexplored ground is clo.se to and will 
be accessible from present workings. 



240 PLAfKR MINING FOR GOLD IN CALIFORNIA [Bull. 135 

Tlio coinpaiiy is plamiin^- to iiicrcas(^ its lidistiii^ aiul mill capacity 
to ;")()() tons a day, after wliicli miiiiiiu- will he expanded <ri"adiially by 
addition of units of nnderiiround e(|nipinent In ]irovi(le that tonnap:e. 
The company records show that since lli^U it lias mined 185,000 tons 
of material, of which about 75 percent has been auriferous frravel and 
bedrock that have been milled, the balance beiup- waste bedrock. 

Thi-ee channels so far developed in the Calaveras Central property — 
the Aetiui, Central, and Xo. 5 — are said to have yielded $240, $255, and 
$530, i-espectivelv, i)er linear foot. The averajre recovery durin<; 1935 
was $5.17 per ton, and from the b^jiinniuj? of operations in June lf)31 
to ]n3f), inclusive, the avei'ape was $4.94 a ton. These averajres include 
recovei'ies from much low-j^rade fjravel extracted durinp; exploration 
work, which mipht be excluded in breasting- developed reserves. The 
ranjje of values found varied considerably with the character and 
jrrade of the bedrock and the position of the pay in relation to the 
'channels. Rich concentrations were occasionally found yielding an aver- 
ajre as hif>h as $72 per ton for a single day and $18.71 \)ev ton for an 
entire mouth. The rich pay streaks provided many specimens of con- 
solidated p-ravel in Avhich numerous small nujrfrets are plainly visible. 
In one speciment the nujjjrets are all flat and lie, with reference to each 
other, precisely like shingles on a roof. Such ricli concentrations illus- 
trate the effectiveness of bedrock as a riffle under some circumstances. 

The yields obtained do not represent the total L'old content of tlie 
prravel, as considerable tailiufrs losses occurred. About 42,000 ton.s of 
fine tailinjrs have been ])roduced since miniuqr bepran in 1931. Of these, 
12,000 tons were re-treated and yielded $1.35 per ton with incomplete 
recovery. It is thoujiht that the remaininn' 30,000 tons contain about 
$2 per ton. This would pive a gold content of $84,000 for the fine tail- 
inp:s, to be distributed over the total of 140,000 tons milled, pivinjr 60 
cents a ton. Added to the average of $4.94 per ton recovered, $5.54 
per ton is indicated as the average gold content of all gravel mined 
by the present company, exclusive, of course, of any lost in the coarse 
tailings. 

Mining and Milling 

The room-aud-pillar method of mining is used. Bedrock drifts, gen- 
erally under the rims or in the troughs of the cliaunels, are used as 
haulageways. 

The gravel face and 1 to 3 feet of the bedrock are shot doAvn with 
light loads of 40-perceut dynamite. In past operations the product 
has been loaded into 2-ton cars largely by Eiinco-Finley loaders. Light 
drifters were used for drilling. The loaded muck was hauled to the shaft 
by storage-battery locomotives, generally in trains of four to .six cars, and 
dumped into a gravel j^ocket, from which it was drawn into 2.i-ton skips 
and hoisted. The skips were dumped automatically into a 70-ton mill 
bin adjoining the head frame. Waste was delivered to a 20-ton bin, from 
which it was discharged by a 200-foot stacker with a 24-incli belt. 

In the milling system used for most of the past production the 
material in the bin was fed to a 21- by 5-foot cylindrical washer with 
a 10-foot puuched-plate screen section having 1-inch holes. The over- 
size from the waslier was piled by a 275-foot stacker having a 24-inch 
belt. The undersize passed through a specially designed sluice and 
gold trap 24 inches wide and then through a second sluice 12 inches 



Sec. IV] 



MINi:S RY COUNTIES 



241 



wide and 24 feet !<)n<r, lined with Ilunfrarian riffles. The discharge 
from tlie sluice was dewatered by a draf? classifier and conveyed to a 
Leahy vibratinjr screen, which made three products — plus J-inch mater- 
ial, which was piled by a loO-foot stacker havin<r a lO-incii belt; minus 
^-inch but plus i-inch ; and minus i-inch. The two smaller sizes were 
treated in a Huelsdonk concentrator, the dischar^re from which was raised 
by a bucket elevator to a launder, which conveyed it to the fine-tailings 
dump. 

The washing plant described is now being dismantled, as the com- 
pany plans to replace it with a plant of 500 to 600 tons capacity. 

The present double-drum hoist has a capacity of 1,000 tons a day. 
Two Sullivan angle-compound compressors of 400 and 800 cubic feet 
capacity, respectively, supply air for drilling and the operation of com- 
pressed-air machinery. The mine makes about 150,000 gallons of water 
daily, which is pumped from the shaft sump by a 50-horsepower, Sterling 
vertical turbine pump into a 100,000-gallon tank on the hillside above the 
mill. This tank supplies ample water for milling. The property has a 
large change room, a blacksmith and machine shop, a first-aid building, 
oiifice, and other structures. The number of men employed has ranged 
from 30 to 70, but this number will be doubled under the contemplated 
expansion program. 
Costs 

The following table shows the average daily mining and milling 
costs during 1933 and 1934, a period selected because of the wide range 
in the average daily tonnage treated. The costs given cover the mining 
and milling of gravel and auriferous bedrock and the mining of waste 
bedrock, the latter usually amounting to 25 or 30 percent of the total. 
The daily tonnages range from a high of 209 tons in May 1933 to a low 
of 41 tons in May 1934, the corresponding working costs being $1.40 and 
$3.04 per ton, respectively. The adverse eifect of the inverse ratio is 
at once apparent. 

The costs given include labor, compensation insurance, power, 
explosives, lubricants, and salaries of the general manager and super- 
intendent. Depreciation, depletion, and other overhead co.sts are not 
included. 

^fit^ing and milling costs at the Calaveras Central mine from January 1933. 
to December 193'i, inclusire 



Monthly 

gross 
tonnage 



Average 

daily 
tonnage 



Mining 
and mill- 
ing costs 

per ton 



to^nTge 1 tota^e | -f -'« 



January-.. 
February.. 

March 

April 

May 

June 

July 

August 

September 
October... 
November 
December. 



3,399 


109 


3,719 


132 


5,433 


175 


5.472 


182 


6.507 


209 


5,753 


191 


4,313 


143 


3,315 


106 


3,137 


104 


2,526 


81 


2.471 


82 


3.491 


116 



$2.27 
2.11 
1.73 
1.61 
1.40 
1.54 
1.73 
2.02 
2.03 
2.52 
2.60 



January . . . 
February.. 

March 

.\pril 

May 

June 

July 

August 

September. 
October... 
November. 
December - 



Average. 1933 and 



4.363 


.40 


3.056 


109 


2.234 


72 


1.264 


42 


1,271 


41 


1.645 


54 


2.440 


81 


3.114 


100 


3.350 


ni 


4,203 


135 


4,087 


136 


2.856 


95 


3.476 


114 



$1.64 
1.88 
2.30 
2.73 
3.04 
2.74 
1.85 
1.91 
1.84 
i.54 
1.63 
2.31 



242 



pi.a(i:r mininc fok oold in rAi.ipoRXiA 



IP.nll.lM.-) 



Tilt' very iirc^iiilar i-atc of production indicates that development 
or equipment was inadecpiate to maintain steady production necessary 
for holding costs at a low level. Durin^r the 2-year period 83.41!) tons 
of material was mined, an avera<;e of 114 tons a day, at a total cost 
of $ir)7,()f)9 and an averajre cost of $1.89 per ton. 

Hased upon an analysis of cost details, the manafrement has esti- 
mated that if the output had averajred 200 tons daily, the correspond- 
ing' cost would have been $1.40 a ton, which was actually attained 
in May lf)33; that at 300 tons a day the correspondiufi cost shoidd 
be about $1.2") a ton; and that at ")()() tons a day about $1 mijrht be 
attained. The tenor of these conclusions is obviously correet. There 
remains, however, the question whether the larger rates of produc- 
tion can be maintained .steadily. If so, it would be accompanied by 
some lowerinj; of average grade, as low costs would naturally induce 
the mining of greater w^idths, including the low-grade gravels of the 
channel margins, and perhaps abandonment of all selection within the 
channels proper. This Avould exactly parallel the usual trend toward 
nonselective mining that proves inevitable in lode mines. 

Even now the costs attained compare favorably with those current 
when drift mining was at the height of its prosperity, when much clieap 
labor was available. Then, under favorable conditions for mining and 
milling, cemented gravel was worked at a cost of from $1.73 to $3.50 
a cubic yard, eciuivalent to $1.16 to $2.32 a ton."* 

Character of Production 

The gross tonnages do not, of course, consist entirely of pay gravel 
or income-producing product. A certain proportion must be bedrock 
waste, taken out in running approach and haulage tunnels, and the 
proportion of such material to the pay gravel has an important etfect. 

In mining 185,000 terns of material, 75 percent was gravel and 25 
percent waste. As the gross tonnage increases, the proportion of waste 
decreases, because in a small-tonnage operation the gravel is mined 
more selectively to offset high cost. To maintain this liigh average 
grade there must be constant additions to the main haulage system in 
order to pass through or around low^- or even medium-grade gravel to 
reach the grade being mined ; but in an operation where the daily tonnage 
is large and the cost lower, the gravel need not be mined so st>lectively, 
and its bulk in proportion to waste becomes greater. 

The general et!"ect of increased tonnage in reducing the percentage 
of waste is thought by the management to be somewhat as indicated 
below. For 100 and 200 tons the figures are based upon records; for 
the higher tonnages they are estimates as to effects that might be 
rea.sonably expected. 



Daily production 


Waste 


Gravel 


Pay 
material 


lOOtons ... 


Tons 
30 
40 
50 
60 
70 


Tons 
70 
160 
250 
340 
430 


Percent 
70 


200 tons 


80 


300 tons 


83 


400ton8 . 


85 


500 ions 


86 







* Hammond, John Hays, The auilferou.'* gra> 
Min. Bur., State Mineralogi.sf.s Rept. 9, p. 119, 1889. 



)f <\ilifornia: California State 



Sec. IV] MIXES BY COUXTIES 243 

The use of mechanical h)a(lers in this mine has been an important 
means of reducing: costs. To obtain from them the benefit of con- 
tinnous operation, empty ears mnst always be at the face for loading. 
Switch si)urs are therefore driven at frequent intervals as the headings 
are extended, to aid in placing cars. Usually these spurs develop later 
into crosscuts or other haulageways. Sometimes, however, cars are 
lifted bodily and transferred to the end of the train by means of a device, 
developed at this mine, that may be called a car derrick. It consists 
of a 6-inch I-beam, about 9 feet long, with a l-ton, geared chain hoist on 
a carriage that rolls on the lower flanges of the beam. The beam is 
wedged securely at each end into niches cut in the walls near the roof, 
or it may be supported partly by .stulls. A steel spreader with hooks 
at each end depends from the hook of the chain hoist. The hooks are 
swung under either the ends or sides of the car and it is lifted a few 
inches off the track and pu.shed into a shallow rece.ss in the wall, far 
enough to clear the train. When the locomotive has pulled the train 
by, the empty car is returned to the track. Use of this derrick is said 
to save a great deal of time and expense that would be required to pre- 
pare switching spurs. It is especiallv useful in driving long bedrock 
drifts. 

The great savings effected by mechanical loading underground have 
led the management to devise a system of mining that seeks to utilize 
it to the utmost. The following notes concerning this and other means 
of reducing costs and increasing efficiency are condensed from data 
furnished by Harry Sears, general manager. 
Technology of Drift Mining 

The gravel is tightly cemented ; bedrock drifts usually hold firm 
without timbering, hence both gravel and bedrock are treated like hard 
rock of a lode mine. The mine is being laid out with the object of 
opening it in a number of sections with separate equipment provided 
for their operation. Enough of them are to be provided to assure pro- 
duction of the mine as a whole at a steady rate and to permit the sections 
to remain idle after blasting long enough for the smoke to be dispelled. 

The workings are planned so as to permit good circulation of air, 
and many crosscuts and connecting drifts have been run for this pur- 
pose, which, incidentally, have served as exploration drifts. In most 
eases the efficiency gained through the better air conditions has largelj^ 
paid for the exploration drifts. 

Headings generally are 7 by 7 feet. Drifts are run on a grade of 

1 percent to assure drainage away from the faces, except in very wet 
gravel with considerable sand, where the grade sometimes is increased 
to 2 percent, as otherwise the sand would settle on the tracks and too 
much time would be lost in keeping them clear. Normally there is 1 to 

2 feet of bedrock in each gravel face, the rest of the 7 feet being gravel. 

The whole of the face is drilled, usually with 8 to 10 holes 6 to 7 
feet deep. Most of the headings are loaded out with mucking machines 
and, before shooting, the rails with slide rails in place are brought 
practically up to the face. The holes are loaded and shot so as to deliver 
the muck, combined gravel, and bedrock in a compact pile close to the 
face. It is therefore a simple matter to bring a loader into the heading, 
clean up the track, and quickly reach the main muck pile. The slide 
rails are advanced as needed, the lip of the loader scoop being used to 
push them under the muck when required. 



244 PLACFR MrNINP, FOR GOM) IN CALIFORNIA fBllU. 135 

Many areas have been Avorkcd by driving'' roti^dily i)arallel drifts 
with lon^' walls botweon th(Mn, these walls later beinj:- shot throu'^h at 
refrular intervals to form pillars. This was done with the tracks in 
both drifts in place, and nearly all of the muck was handled with the 
loaders. For this work the track is laid on Hat steel ties, and it can 
be slid or barred over from its ori<rinal jiosition when re((nired. Con- 
siderinjr each of these workin<r ai-eas as a room containinp: a number 
of pillars or walls, if it is desired to mine it out completely and retreat, 
this can be done by pointinjr the track at individual ])illars as they are 
finally sliot out. and takinp- up and shortenin«r the track while retreatinp: 
to the entrance of the room. Stulls with headboards or caps may be 
required to support the <iround while the final pillars are being .shot 
and loaded out. but often they are not. 

The loaders have also been used on longwall work, by drillinpr the 
wall and sliding tlie track over almost against it so that the muck will 
be thrown on the ti-ack. In all of these methods a moderate amount of 
hand-sliovel work is necessary to clean U]i completely spots beyond the 
radius of the loader scoop. The best method of handling each mining 
area must, of course, be determined somewhat by the character of the 
ground. 

All of the muck is loaded, and no boulders are separated or piled 
underground. The old practice of piling boulders underground recjuires 
much hand labor and is far more expensive than bringing them to the 
surface. Of cour.se, very large boulders must be bulldozed or broken 
with sledges before they can be loaded out. and occasionally some of these 
larger bouldei-s are left underground. l)ut never piled up as Avails. The 
bedrock is never scrai)ed. but is shot and treated as gravel, being taken 
to sufficient depth to get all the gold in its crevices. 

Work with a multiple-track system not only provides several head- 
ings for loading in a comparatively small area, but makes it possible 
to maintain switches close to the faces, so that empty ears may be readily 
available and the loaders can be kejit in steady ojieration. 

In driving long, single-track, bedrock haulage drifts by means of 
a car derrick, several thousand feet of drifts have been driven at the 
rate of 18 feet per day. with two men in each heading, three shifts per 
day. Each shift drilled, shot, and loaded out the muck for a ()-foot 
advance and did the necessary ti-ack and jiipe work. Each crew of two 
men. however, was assisted by a motorman who brought in the empties 
aind took out the loaded cars. Two-ton cars haided by storage-battery 
locomotives were used. The motorman 's services were only required 
during an api)roximate 1-hour |)eriod while mucking out. Tiravel load- 
ing does not generally proceed as fa.st as this, particularly with the 
room-and-pillar woi-k described, for considerable time is re(|uired to 
break large boulders, place stulls. and do track and hand-shovel work. 
For most rapid work, the loaders must be kept on .straight tracks for 
they are slowed materially when on curves. The foregoing remarks 
apply to the use of Eimco-Finlay loaders, which operate within a fixed 
radiu.s along or fr(»m the end of the track, and which throw the muck 
back into a car that is coupled to the loader and moves with it. 

A Nordberg-Butler shovel on a caterpillar tread also has been used. 
This shovel is very efficient in room work where a train of several cars 
can be delivered on the track, and the shovel can load them all without 



Sec. IV] MINES BY COUNl-IES 245 

spotting? or shift iiij: them. AVith its ability to move around on both 
sides of tlie cars and its consequent wide loading: radius, this shovel has 
distinct advantajres while workinj? in a prescribed area, but much more 
time is re(}uired to move it from place to place in the mine than with 
the Eimco-Finlay loaders. 

In openin<r various channels and preparing multiple sections of 
each for production, the management endeavors to maintain independent 
haulage drifts, preferably beneath the lowest point of the channel 
troughs; or, if this cannot be done, then in the bedrock rim alongside the 
channel. If it is necessary to pass through the gravel itself, the drifts 
are kept as much as possible in low-grade gravel. With this system, 
entrance may be had to the channels from any required point in the 
haulageway and as much or as little gravel extracted as desired without 
impairing the efficiency or adding to the upkeep of the main haulage 
system. Another point of advantage is that good gravel need not be 
tied up indefinitely to keep the haulage drifts open. 

"Where the main haulageway is deep enough below the gravel to 
permit it, entrance to the gravel is made through a raise and a bin is 
built, which can be loaded as required from the upper level and drawn 
when convenient by the train crew on the haulage level. Where the 
difference in levels is only 5 or 6 feet, transfer platforms are built to 
accommodate at least three cars, and these are loaded directly, either by 
'center or side dumping, from the cars above. Car loading with drag 
scrapers is invariably done by dragging the load onto a platform beneath 
which a car is spotted, the load being delivered directly into the car 
through a slot in the platform. 

Drag Scraping. A particularly interesting phase of mining at this 
property has been the work done with drag scrapers — probably their 
first use in drift mining. Though only a small tonnage has been handled 
by this method, it has been sufficient to establish facts on procedure and 
costs and its use is to be extended. The following is intended to be 
merely suggestive of possibilities foreseen. 

In prepared ground, ninety 2-ton cars were loaded with a small 
scraper by three men during an 8-hour shift. It is estimated that four 
man-shifts were required to prepare the ground by drilling and shooting, 
that one man-shift was utilized for electric tramming, one-half man- 
shift for drawing into the skips, and one-half man-shift for hoisting, a 
total of nine man-shifts for drilling, shooting, loading, tramming, and 
hoisting 180 tons, a production of 20 tons per man-shift. 

xVssuming a labor cost of $5 per man-shift, including compensation 
insurance, the cost delivered in the mill bin was $45. Adding one man- 
shift for milling and sluicing gives a total direct labor cost of $50. With 
an allowance of $15 for explosives, power, and incidentals, the mining 
and milling cost for the 180 tons handled is estimated at approximately 
$65, or 36 cents per ton. 

It Ls thought that Avith a heavier scraper and larger cars this pro- 
duction could have been increased 50 percent with additional expense 
of two man-shifts for drilling, one-half man-shift for tramming, one-half 
man-shift for drawing into skips and hoisting, and one-half man-shift 
for milling, making an additional three and one-half man-shifts, costing 
$17.50. With $7.50 added for explosives, power, and incidentals, a cost 
of $90 for mining and milling 270 tons of gravel, or 30 cents per ton, is 



246 PLACER MINING FOR GOLB IN CALIFORNIA [Bull. 135 

indicated. To the foregoing costs must be added the proportion of 
expense properly chargeable to the ground, iiicludinfr approach and 
installation work. In handling: caved gravel, drilling and shooting 
costs are eliminated. 

Unfortunately, however, the application of this method has limits, 
experience gained at this mine indicating that drag scraping in drift 
mines is suitable only for areas present ii;g certain favorable conditions 
of bedrock and of the gravel body itself where a large prepared tonnage 
can be made available. It i.s expected that this method will find its 
principal use in handling large toiniages of low-grade gravel, but that in 
many cases it can also be used for mining the high-grade gravel remain- 
ing after all the ground that can be mined safely by other methods has 
been taken out. 

The preparation of ground for scraping entails considerable dead 
work. The gravel should first be opened and tiioroughly drained, as 
scraping can be done best in dry ground and water on the bedrock cau.ses 
a loss of gold in scraping. In dry ground more gravel is broken per shot. 

For safety, the tail pulley and the tugger hoist should be placed 
where there is no danger from caving, and they should be accessible 
through drifts or raises independent of the scraping area. Tiarge 
scrapers and powerful tugger hoists are desirable, as the essence of suc- 
cess in scraping is quantity, and with heavy e(|uipment the same number 
of men can load a much larger tonnage than they can with light ecjuij)- 
ment. There should be an ample supply of both cars and locomotives, 
for when loading is done by this method empty cars, preferably of large 
capacity, must be constantly available. 

Hoisting and milling capacities must be suitable for handling the 
large tonnage necessary for operating on low-grade gravel. Otherwise, 
they must be used for gravel of higher value. In future operations it is 
thought that a tonnage balance will be worked out between high- and 
low-grade gravels. 

Under .some roof conditions drag scraping can best be used after the 
graveLis partly or largely worked out by drifting, and has then been 
caved or has been allowed to cave of itself to a limited lieight before 
scraping is attempted. 

Reserve scrapers and cables must always be kept on hand, as they 
may be buried by caving under conditions that will prevent men from 
safely entering the room to recover them. Occasional losses of this 
equipment should be taken as a part of the cost of using the liiethod. 

Project for Improvements 

During forthcoming construction of a new plant, the management 
plans a number of fundamental changes underground as well as on 
the surface. 

The shaft is to be entirely retimbered. new water, air. and jiower 
lines installed, and the shaft deepened to create a larger sump and 
provide additional depth for drawing from gravel and waste pockets, 
each to be enlarged to 100 tons capacity. A .separate gravel pocket 
will be provided for tonnage for sampling and testing. The bins will be 
arranged so that the cars on an incomiiur loaded train may be dumped 
into their respective pockets without disturbing the make-up of the train. 

A new, 50-hor.sepower, Sterling, vertical turbine mine pump is to 
be installed and mounted on a roller carriage, so that when motor or 



Sec. IV] MINES BY COUNTIES 247 

pump repairs are necessary the complete unit may be disconnected, 
brou<rht to the center of one of the hoisting compartments of the shaft, 
hooked onto the bottom of the skip, and brou<»ht to the surface. 

Heavier rail will be laid throupfhont the main-haulape drifts and 
the track jrajie will be widened to permit the use of low-slung:, 3-ton, 
drop-bottom cars. Trolley locomotives will be used for main haul- 
age, and storage-battery locomotives in newly opened ground and for 
gathering and train make-up. New 3i-ton skips will be provided in 
the shaft for hoisting both waste and gravel, with screened cages above 
them for raising ancl lowering the men. 

A new steel headframe 100 feet high will replace the present 65-foot 
wooden one. For surface storage, a 400-ton bin will be divided into 
three compartments — 250 tons for the regular production of gravel, 
75 tons for gravel to be sampled or tested, and 75 tons for waste. 

The gravel will be delivered from the bins by magnetic vibrating 
feeders, which will assure the regular feed essential for proper mill- 
ing. In order that the cemented gravel may be completely disinte- 
grated and the gold liberated from it. the gravel must be subjected 
to much attrition and scrubbing. In the old washing plant the trom- 
mel did not retain enough water to effect complete scrubbing of the 
gravel, so a watertight cylindrical washer will be installed, which will 
carry a much larger load than the old trommel. In this the bulk of the 
material will be immersed in water, and the grinding and scrubbing 
action of the gravel and boulders is expected to produce a much cleaner 
product. Breaking up the larger cemented pieces does not present as 
much of a problem as does material between one-sixteenth and three- 
eighths inch in size. The greatest loss of gold in the tailings in the past 
has been in this size of material in which light flakes of gold adhere to 
bits of gravel or light sulphides or are encased therein. It is thought 
that this loss may be eliminated by the increased grinding and scouring 
action of boulders in the new scrubber; but if it is not. this fine material 
will be separated by screening, to be returned for re-treatment or to 
be ground separately. 

The coarse gold, constituting the principal part of the clean-up, 
will be recovered as in the past in sluices immediately following the 
scrubber. The sands and fines will be fed in a thin flow to Pan American 
jigs, which will make a rough concentrate in their hutches ; this will be 
cleaned by another jig to a final concentrate consisting of fine gold 
and black sand. This concentrate may be shipped for final recovery of 
its values to a plant treating black sands from dredges. The coarse 
material discharged from the mill will be piled by stacker belts, the 
fines being delivered by launders to the tailings pond. 

A pilot mill will duplicate the processes of the main washing plant. 
Its function will be to make batch runs of 10 to 30 tons of gravel, so 
that any face in the mine may be separately sampled. Such large-lot 
sampling will determine how far mining may be profitably carried into 
areas of questionable value, and will serve as a constant check upon 
the average gold content of the mill tonnage. 

Vallecito Western Drift Mine 

The Vallecito Mining Company. Inc.. Murphys, worked the Val- 
leeito-Western drift mine throughout 1940 and recovered 221 ounces 
of gold and 25 ounces of silver from 685 cubic yards of gravel. The 



248 PLACER MINING FOR GOLD L\ CALIFORNLV [lUlll. 135 

followiiiji' (l('Sfrij)tion of this iiiiiio is roi)riMted from V. 8. Bureau of 
Mines Bulletin 413.'' 

The \'all('eito-\Vestei'u mine is 3 miles east of An;.aMs Camp in 
See. 24. T. 3 N., R. 13 E. It is on the same ehannel as the Calaveras 
Central mine, about 2 miles dov.nstream ; and the (Jolden River mine 
adjoins it upstream. This is the Central Hill or main ehannel of the 
Tertiary Calaveras River. The property is owned by Thomas B. Bishoji 
Co., 1G() (Jeary Street, San Fi'aneiseo, but is luider lease to the Valle- 
eito Minin<i- Comi)any, of which Don Steffa, of ^lur])hys. California, is 
general manajzer. However, from Deeember l!)32 to October l!)3(i the 
mine was operated under sublea.se by the Tonoi)ah-r>elmont Develop- 
ment Comj)any under the dii-ection of Frederick Bi-adshaw. of San 
Francisco, and the operatiii<:- data uiven herewith cover most of this 
period. 

Since the mine was opened in 1!»'2.') it has produced over .$400, ()()() 
in ^old, reckoned at its present priccv It is develojied by a KiT-foot 
vertical shaft with a 4- by 4;l-foot skipway ami 2.1- by 4-foot manway. 
This shaft was completed in May ]!t24, its site havinu' been determined 
by a line of seven churn-drill holes sunk across the chaiuiel. The shaft 
passed throuj-h about .lO feet of white rliyolite cobble and ash and then 
entered a bed of well-rounded, bluish jiravel made up larjicly of j^or- 
phyritic malei-ial ;iii(l containinii' fre(|uent beds of sand and volcanic 
ash. Near the Ix'drock the ])oi-phyr\- uraxel disappears, and the ]->ay 
gravel is largely made u]) of granite with a small i)ro])oi;tiou of (puirtz, 
quartzite, jasper, and slate. Pieces of chocolate-brown semipetrified 
wood are sometimes found in the i)ay gravels. 

At a depth of l.')3 feet, a tunnel on bedrock runs upstream from the 
shaft station for 300 feet and then, after a vertical I'aise of o feet to 
surmount an abrupt rise in the bedrock, it continues on a 1 ] -percent 
grade for 4,000 feet. This tuuiud serves as a haulageway and drain. 
At the shaft the bedrock is slate, but it changes upstream first to gi-ano- 
diorite and then to granite cut by bauds of grauodiorite. As the grade 
of the bedi-ock is slightly greater than the tuuiuH grade, jiai-ticularly 
in its ui>stream end. the tuiuiel gradually pa.sses into the bedrock, and 
access to the gra\el above is gained by shoi-t raises used as chutes. The 
spacing of the rai.ses depends on the volume of the gi-a\el that is to be 
extracted through them and on the contours of the bedrock. Where the 
gravel is mined for widths of 100 to l.'iO fe(>t the raises may he only 
50 feet ai)art. but in uari-ow workings the distance Ix-twecn tlit'm ma.\- 
be as much as 125 feet. 

The gravel is mined by bi-east stoi)iug across the full width of 
the paystreak. which raiiges from 40 to 150 feet and is exti-acted for 
an average lieight of (5 feet. Two rows of (J-foot holes, spaced 4 feet 
apart in th(> row. are drilled in the gi-avel faces, the lower one 1.] 
feet and the upper one 3^ to 4 feel above bedrock. The.se holes, loaded 
with three or four sticks of 40-pei-cent dynamite, bi-eak to a height of 
5 feet. H" a greater height is mined, to include an occasioiud i)aystreak 
well above bedrock, an additioiud row of holes is drilled. (Jenerally 
75 percent of the gold i-eeovered is on the bedi-ock or within a foot of it. 
"When the bedrock is soft or badly ci-eviced. 1 to 2 feet of it are mined. 
Such a eondition occurs where the bedi-ock is slate or grauodiorite, but if 
the pay-lead actually rests on bedivx k e\en a giauite bedi-ock is taken uj). 

■Juiihii, C E.. and Hurlon. F. \\'., oi'. (it. 



Sec. IV] MINES BY COUNTIES 249 

The gravel is well-rounded and heavy and contains many large 
boulders, which are piled underground in niined-out areas. Huge 
boulders 6 to 10 feet in niaxinuini diameter occur frequently, and 
these are mined around; but if they are too much in the way they are 
drilled and broken. Normally the gravel is not cemented but stands 
well. However, in some places it must be held by square-sets, though 
usually posts 10 to 12 feet apart, with headboards, furnish ample support. 

The broken gravel is loaded at the face into wheelbarrows and 
dumped into the nearest chute, from which it is drawn into 1-ton ears 
that are hauled, in trains of four, by a storage-battery locomotive to 
a car dump at a point 300 feet from the shaft, where the bedrock rises 
abruptly. Here it is transferred to other cars trammed by hand to the 
shaft, where they are discharged directly into a l^-ton skip. 

The shaft has a 76-foot head frame Avith a built-in, -SO-ton ore bin. 
The skip is operated by a 50-horsepower electric hoist. An IngersoU- 
Rand compressor, belt-driven by a 60-horsepower motor rated at 355 
cubic feet per minute, supplies air for drilling. About 100,000 gallons 
of water per day is pumped from the shaft .sump by a Sterling electric 
pump with a capacity of 135 gallons a minute. Pumping 12 to 16 hours 
a day handles the water. 

The mine is well-ventilated. A 12-ineh churn-drill hole from the 
surface intersects the haulageway about 2,400 feet from the shaft and 
has a down draft providing fresh air. A blower .sends air from this 
point through 12-incli galvanized irou pipe to the tunnel face and the 
active mining areas. 

The gold at the Vallecito-AVestern property is coarse and averages 
895 fine. The balance is almost entirely silver. Ninety percent of the 
gold by weight stays on a 20-mesh screen. Nuggets having a value of 
$1 to $5 are common, and many worth from $10 to $20 have been found. 
The largest nugget yet discovered weighed a little less than 10 ounces. 

Washiyig Plant. The washing plant adjoins the shaft. Gravel from 
the head-frame bin, into whit-h the .skip discharges, falls by gravity into 
the upper end of a sluice 12 feet long and 2 feet wide, where it is washed 
by only sut^cient water to move rocks 4 to 5 inches in diameter. Larger 
rocks are picked from the .sluice by hand, thrown into a car on a lower 
floor, and trammed to the dump. Fifty to sixty percent of the gold is 
recovered in this short sluice. The finer gravel flows into a revolving 
washer 36 inches in diameter and 9 feet long, making 35 revolutions per 
minute. This washer has a 4-percent slope and is equipped with lifting 
plates, which elevate the gravel and then let it fall, thus breaking lumps 
and scouring off adhering clay. A 4-foot double trommel of punched 
steel plate is attached to the discharge end of the washer. The inner 
screen is 20 inches in diameter and has l|-inch round holes. The outer 
screen has one-half inch holes and is 36 inches in diameter. Plus 1^-inch 
gravel is sluiced to the dump, but the two finer sizes are washed in 
separate sluices. 

These sluices are 1 foot wide inside and have a 4-percent grade. 
They are lined with riffles of a novel design, which are very effective 
in preventing packing and also in retaining the gold. These riffles are 
of bar iron 15| inches long, 2 inches wide, and a quarter of an inch thick, 
bent at right angles 2 inches from each end and the bent portions beveled 
and drilled. The drill holes receive rivets that fasten the riffle to the 



250 



PLACER MINING FOR GOLD IN CALIFORNIA 



Bull. 135 



sluice liners. The bar sits at an an«rle of 45° agrainst the current and its 
upper edge forms a lip that produces a distinct boil in the pocket beneath 
it. The lower edge of the riffle face does not contact the bottom of the 
sluice, but the intervening space fills in with small pebbles, which keep 
the gold from sliding along the bottom of the box. 

Some loss of gold occurs in the washing plant when pieces of 
cemented gravel are discarded by the trommel or go through the sluices. 
However, relatively little cemented ground is found in the workings, 
and this is segregated and allowed to air-slake before it is washed. 

The recovered gold averages about 0.17 ounce, or $5.95 per ton of 
gravel washed, but it varies, of course, within wide limits. In August 
1936, 80 tons of gravel were mined and washed per 24 hours. Twenty- 
five men were employed on three shifts. 

The following tables show the production and costs at the mine foi* 
a period of 45 months ended September 1, 1936. In interpreting the 
costs, it must be remembered that they are based on the tonnage hoisted 
rather than on tonnage mined. The waste hoisted was equal to 44.2 
percent of the gravel milled. Most of this waste was derived from bedrock 
cuts, and the rest consisted of boulders which it was necessary to hoist 
wherever new breasts were started, until enough room was cleared to 
pile them back of the face. About 30 percent of the ground mined con- 
sisted of boulders, which were left underground, so the total waste mined 
approximately equaled the tonnage of gravel milled. 



Costa and production of the Tallecito-Western mine, ^o months, to September 1, 1936 

Tons 

Gravel mined and milled 40,967 

Waste hoisted 18.102 

Total gravel and waste 59.069 





Value 




Total 


Per ton of— 




Gravel 


Gravel and 
waste 


Production: 
Gold, 7,222.5 ounces 


$232,268.00 
492.00 


$5.6696 
.0120 


$3.9321 


Silver, 814.9 ounces 


.0083 








$232,760.00 
11,713.00 


$5.6816 
.2860 


$3.9404 


Loss in tailings 


.1984 








$244,473.00 


$5.9676 


$4.1388 






Corts: 

Mining and milling during— 
Development 


$62,747.05 
84.111.17 
14.302.64 
13,344.31 
13,064.07 


$1.5316 

2.0531 

.3491 

.3257 

.3190 


$1.0623 


Breastmg 


1 4239 




.2421 


Water supply 




Compensation insurance 


2212 






Total of direct mining and milling 


$187,569.24 
19.852.06 
1.171.73 


$4.5785 
.4846 
.0286 




Indirect mining and milling 


3361 


Marketing (mint charges, etc.) 


0197 






Total operatmg coat 


$208,593.03 

$24,166.97 

24,946.00 

779.03 


$5.0917 

$.5899 
.6089 
.0190 




Profit before payment of royalty 


$.4092 


Royaltiea 




Urn 









Sec. IV] MINES BY COUNTIES 251 

The marginal character of drift mining, when conducted as described, 
is well-illustrated by these data of costs and production. With an aver- 
age gold content of $4.14 per ton of gravel and waste hoisted, which 
becomes $5.97 per ton for gravel alone, the actual recovery is $5.68 per 
ton of gravel. However, this very substantial recovery exceeds the 
operating cost of $5.09 per ton of gravel by only 59 cents per ton, while 
royalties amount to nearly 61 cents per ton, so that .there is a final loss 
of nearly 2 cents per ton of gravel. The net result is merely the mainte- 
nance through 4 years of the labor employed and payment of the royalties 
required by the owner of the ground, while no excess is left to reward 
the operating company that carried the burden of responsibilities. 

The rate of production is very low, however, averaging a trifle less 
than 30 tons of gravel per day for the whole period. It is immediately 
obvious that a marginal operation at that low rate of production would 
probably become profitable at a higher rate of production. That, in 
turn, would require an additional capital investment and probably a 
preliminary determination of the underground contours of the channels 
in order to plan with certainty production adequate for profit. 

Such determinations have been virtually impossible in the past 
because of the lack of any known method for their accomplishment except 
at prohibitive cost. If, however, it should prove that the buried channels 
of the ancient placers can be mapped completely by geophysical methods, 
the mining of such properties as this should no longer prove marginal 
but should yield substantial profits. 

A portion of the gold mined during the period under consideration 
was marketed before its present price was attained, and the average 
received was $32.15 per fine ounce. 

The early history and operation of this mine under the management 
of the Vallecito Mining Company has been described in an information 
circular of the Bureau of Mines.^ 

Other Mines 

Bacon, E. A., 303 Delmar Way, San Mateo, recovered 286 ounces 
of gold and 14 ounces of silver from 10,000 cubic yards of gravel near 
Wallace in 1942. Hydraulicking and a mechanical excavator were 
used. 

Barson Mining Company, 2054 University Avenue, Berkeley, 
operated a dry-land dredge on the Foster Ranch in the Camanche dis- 
trict intermittently in 1941. Recovery from 55,200 cubic yards of 
gravel was 495 ounces of gold and 37 ounces of silver. (See Cat Camp 
Placers also.) 

Calaveras Central Mine. See page 235. 

Cat Camp hydraulic mine was operated by J. E. Biallas of Valley 
Springs in 194p. Operation of a nonfloating washing plant, for 6 months 
of 1941, to which gravel was delivered by a carry-all, yielded 605 ounces 
of gold and 34 ounces of silver from 100,000 cubic yards. In 1942, Cat 
Camp Placers and Burson Mining Company produced from this mine 
483 ounces of gold and 32 ounces of silver from 71,818 cubic yards of 
gravel with nonfloating washing plants. 



« Steffa, Don, Gold mining and milling methods and costs at the Vallecito-Western 
drift mine. Angels Camp, Calif. : U.S. Bur. Mines, Inf. Circ. 6612, 14 pp., 1932. 



252 PLACER MINING KOR GOLD -IN CALIFORNIA [Bull. 1.'}') 

Church Union mine (Kraeiner) in see. 26, T. 5 X., U. 11 E.. M. D., 
is owned by J. J. McSorley and Thos. E. McSorley, Mokehinine Hill. 
It includes 80 acres of mineral rip:lits and :^0 acres surface ri<rhts on the 
same {rround, containing the Cotfee-Mill channel, which runs in an east 
and west direction. According: to J. J. McSorley, 20 acres of this fjround 
is virprin, and should yield about an ounce of <rold per cubic yard for 
a 6-foot cut on bedrock. A tunnel 1000 feet lonjr has been driven in 
bedrock beneath the channel. 

Clark, U'., subleased the Val Ranch in 1942 and operated a. statioiuiry 
washinpr plant, to which -rravel was delivered by power .shovel and trucks. 
From May 7 to October 19, the yield was 69 ounces of gold and 7 ounces 
of silver from 6245 cubic yards of gravel. 

.Deep Lead placer mine is in sec. 13, T. 5 N., R. 11 E.. M. D., and is 
owned by Miss Theresa Rooney, 1106 — 3rd Street. Corpus C'hri.sti, Texas, 
who holds 90 acres on the Chili (Julch Blue Lead chamiel. According 
to J. J. McSorley, Mokelumne Hill, about 20 acres of this ground remains 
unworked, and will yield about an ounce of gold per cubic yard for a 
6-foot cut on bedrock. A shaft from 90 to 100 feet deep will be required 
to open the mine. 

Glo-Bar Mines, 370 East 37th Street, Long B'each, operated the (Jlo- 
Bar drift mine in the Campo Seco district throughout 1940. Recovery 
from 4464 cubic yards of gravel was 321 ounces of gold and 44 ounces 
of silver. Operations continued in 1941. 

Gold Hill Dredging Conipan}/, 311 California Street, San Fran- 
cisco, operated an electric connected-bucket dredge on the Arlington and 
Osterman [)roperties along the Mokelumne River during 5 months of 
1941. 

Golden Hirer Mining Conipang, Roland Rich Wooley. })resident, 
915 Transamerica Building, Los Angeles, ha.s operated a dnft mine near 
Vallicita in sees. 21, 29. 30, T. 3 N.. R. 14 E., M. D.. on the same main 
channel of the Tertiary Calaveras River on which are the Vallecito- 
Westem and Calaveras Central mines. This company has also done 
geophysical work and drilling on the adjoining Kentucky placer 2 miles 
northeast of Angels Camp in sees. 23, 2<), T. 3 X., R. 13 E. The Kentucky 
appai-ently contains a mile of virgin channel. The company was pre- 
paring to sink a new shaft on this projierty at the time (Oct. 8, 1942) 
that gold mining was shut down by Limitation Order L-208 of the "War 
Production Board. 

Grnwcll, C. E., Angels Camj). opcratctl a dragline di'cdge on the 
Hogate ranch, 3^ miles north of Angels Camp in 1940. 

Ilenrif, J. //., 740 West Willow Street, Stockton, washed 17,200 
cubic yards of gravel by dragline dredging on the E. A. Marsh proi)erty 
4 miles southeast of Valley Springs between May 30 and July 27, 1940, 
and recovered 137 ounces of gold and 13 ounces of silver. The same 
e<|uipment washed 45,600 cubic yards of gravel on the (Jenochio property 
on the Xorth F^ork of the Calaveras River \\ miles north of San Andreas 
between September and the end of the year; ;}62 ounces of gold and 40 
ounces of silver were recovered. 

Horseshoe Dredging Companij, Mokelumne Hill, ojiei-atcd a drag- 
line dredge on the Calaveras River 2 miles southwest of Jenny Lind 
during 1941 ; also on the Beers, Gertzen, and 0.sborn ranclies. 



RPC. IV] MINES BY rOUNTIKS 253 

Ltnicha Plana (iold Drc(l(/in(/ f'onipan!/ of Caiuaiiche, operated its 
(lre(l<,'e Xo. 2 on Mokelumne River in Calaveras County durinfr part of 
1940. The dredp-e has 84 buckets of G-cu. ft. capacity. 

Loi-(J and Blshoj) (Lobicasa Co.), Box 812, Sacramento, operated 
three drajrline dredires on the Stockton Reservoir property on the Cala- 
veras River '^ miles from Valley Sprin<rs in 1040. The draj^line exca- 
vators used 3-, 1.]-, and l^-cu. yd. buckets respectively. Operation of 
the 3-cu. yd. outfit was continued from July 1 to December 23, 1941. when 
the pround was worked out. 

Mehrten Bros, operated a nonfloating washing: plant, to which gravel 
was delivered by carry-all in the Camanche district from January 1 to 
July 22, 1941. Prom 16,200 cubic yards of gravel, 146 ounces of gold 
and 15 ounces of silver were recovered. 

Midas Placer Company, of Camanche washed 50,000 cubic yards of 
gravel in a dry-land plant between April 14, 1940, and the end of the 
year. Recovery amounted to 659 ounces of gold and 52 ounces of silver. 
During a few months of 1941, high-channel gravel at the Penn gold- 
copper-zinc lode property was worked. 

Quartz Hdl Placers and ^1. W. Ellis, Box 116, Angels Camp, oper- 
ated a stationary washing plant, to which gravel was delivered by a 
power-shovel, on the Quartz Hill property in 1941. Recovery from 
11,270 cubic yards of gravel was 298 ounces of gold and 30 ounces of 
silver. 

R. and M. Mining Company of La Porte operated a dragline dredge 
on Coyote Creek from January 1 to April 15, 1940; the excavator had a 
l]-cu. yd. bucket. 

Ralford Mining Company, operated a dragline dredge with a |-cu. 
yd. bucket on the AVm. P. Iliatt ranch in the Campo Seeo district, from 
February 1 to July 10, 1941 . Recovery from 25,000 cubic yards of gravel 
was 199 ounces of gold and 14 ounces of silver. 

San Andreas Gold Dredging Company, 960 Russ Building, San 
Francisco, operated two dragline dredges each equipped with a 1^-eu.yd. 
bucket in 1940. Gravel was washed at the Airola-Costa, Albert Gut- 
tinger, John Guttinger, Batten, Bishop (Bowling Green), Calaveras 
Cement Company, Reed, Canepa, Byers, Fisher, Xuland, Nuner, Tanner, 
Bishop (Lot 29), and Solari properties. This company, Avhich was sold 
to Thurman and AVright, 960 Russ Building, San Francisco, on March 
7, 1941, operated its two dredges on the Fisher, Ilageman-Huberty, 
Hageman, Lombardi, and Nuner properties in 1941. 

Stagan Mining Company, 1440 North Hunter Street, Stockton, 
operated a dragline drdge on the Hunt and Robie ranches in the Jenny 
Lind district in 1940. At the Hunt ranch 86.000 cubic yards of gravel 
yielded 615 ounces of gold and 37 ounces of silver. At the Robie ranch, 
414,000 cubic yards of gravel yielded 2287 ounces of gold and 145 ounces 
of silver. In addition, a dry-land dredge washed a small quantity of 
gravel on the Robie ranch. 

Thompson, V,\ C, Box 77, Linden, operated a dragline dredge on 
the Calaveras River throughout 1940. In 1941 the dredge, equipped 
with 2^-cu. ydr* bucket, Avas operated for 4 months on the Gregory, Sin- 
clair, and Dickhaut ranches li miles southwest of Jennv Lind. Later 



254 I'LACKH MINMNC FOR (iOLD IX TAUFORNIA fBllll. 135 

ill 1!)4], tlu' outfit was moved to Siskiyou County and operated by Shasta 
l)re(l«,Miiji: Company. 

ThuniKin and \Vn'(/Jif,' Huss Huildiii<r. San Francisco, ojierated 
dra^dine dredjre.s in Calaveras County in 1!)41. (See under Saii Andreas 
Cold I)red<rin<r Company.) 

Tomboy Gold Mines, c/o \V. H. Wise, Kedondo lieadi, California, 
holds WO acres in sec. 19. T. 5 N., K. 12 E., M. D. Aecordinjr to J. J. 
McSorley, Mokelumne Hill, this property contains 8()()() feet of channel 
blocked out but not worked on the Happy Valley Blue Lead. The chan- 
nel is oi)ened by 3000 feet of drifting' from a 4()()-foot incline. The 
channel lias been crosscut each 200 feet and was found to be 250 to 350 
feet wide. Gravel is .said to run rouj;hly ^2 to $3 per cubic yard. 

Vallccito-Wcstcrn Drift Mine. See pa<re 247. 

VuncicI, C. F., Oakdale, operated a dra<?line dredge usinj? a 1 i-cu.yd. 
bucket at the Halter mine 5 miles west of Jenny Lind on Calaveras River 
from February 20 to April 26, 1941. From 87,848 cubic yards of gravel, 
552 ounces of <rold and 27 ounces of silver were recovered. 

What Cheer mine, of 140 acres in sec. 24, T. 5 X., K. 11 E., M.D., is 
owned by Mokelumne Placers, Ltd., Box 156, Plymouth, and contains a 
sejrment of the Chili Gulch Deep Blue Lead <,'ravel channel. Aecordinpr 
to J. J. McSorley, Mokelumne Hill, about 20 to 30 acres on the north 
and 20 acres on the .south have not been worked. The channel is the 
.same as that in the Deep Lead placer mine, which see. Mildred S. Barker, 
and three others, c/o Herbert E.. Barker, 641 Boulevard Way, Oakland, 
own a tract of 170 acres adjoining that contains this channel also. 

WolJioIl Dredging Corporation of Natoma operated a dragline 
dredge on San Domingo Creek during part of 1940. The excavator had 
a 2-cu.yd. bucket. 

Young cf- Son Co., Ltd., Mokelumne Hill, moved 40,000 cubic yards 
of gravel at the Yale and Allyn property to a stationary washing plant 
with tractors and carry-alls between April 9 and Augu.st 28, 1940; 420 
ounces of gold and 37 ounces of silver were recovered. 

'.See also Thurman, C. H., Co.sts in dragr'ine gold dredging: Am. Inst. MIn. Met. 
Kng. Tech Paper 1900, Mining Technology July 1945, pages. 



Sec. TV] MINES BY COUNTIES 255 

EL DORADO COUNTY 

Below are notes on recent (1940-4;^) placer mininfr operations in 
El Dorado County. Further details of mineral resources of this county 
are contained in State Mineralog:ist's Report XXXIV for 1938, includ- 
injr lists of gold mines both quartz and placer, by Lo<;an.^ 

Barker Corporaiion, Box 696, Patterson, operated a dragline dredge 
on the Explorers property in 1942. The yield from 95,000 cubic yards 
of gravel was 754 ounces of gold and 94 ounces of silver. 

Big Canyon Dredging Campany, Box 656, Fresno, operated a drag- 
line dredge with a 3-cu.yd. bucket during part of 1940. During 11 
months of 1941, operations on Deer Creek yielded 3,160 ounces of gold 
and 321 ounces of silver from 540,000 cubic yards of gravel. During the 
first 7 months of 1942, operations yielded 1,269 ounces of gold and 137 
ounces of silver from 250,000 cubic yards of gravel. 

Duffy Property. George L. Duffy, Foresthill, holds placer mining 
claims in sec. 24, T. 13 N., R. 9 E., sec. 3, T. 13 N., R. 11 E., M. D., and 
adjoining sections, to cover a dredging project on Middle Fork American 
River. The river is a line between El Dorado County and Placer County, 
and additional details are contained in the chapter on Placer County. 

El Dorado Dredging Corporation, Greenwood, operated a dragline 
dredge using a l|-cu.yd. bucket on GreeuAvood Creek and on Coloma 
Creek during 1940. In 1941, operations from January 1 to March 6 on 
Coloma Creek yielded 833 ounces of gold and 124 ounces of silver from 
106,078 cubic yards of gravel. Equipment was moved to the Hughes 
property on Rock Canyon Creek, where 338,940 cubic yards of gravel 
yielded 2,630 ounces of gold and 281 ounces of silver. At the end of 
the year the equipment was on Irish Creek. 

General Dredging Corporation, Natoma, operated a dragline dredge 
in 1940 and part of 1941 on the South Fork of American River near the 
point where James Marshall discovered gold in 1848. The dragline 
excavator had a l|-cu.yd. bucket. A second dredge with a 2-cu.yd. 
bucket was operated in this same area near Coloma in 1941. The smaller 
dredge was operated on a site near Shingle Springs during the last 
quarter of 1941. 

Good Luck mine yielded 164 ounces of gold and 22 ounces of silver 
from 23,000 cubic yards of gravel in 1942. 

Greenhorn Dredging Company, Youngs, operated a dragline dredge 
on the Middle Fork of Cosumnes River near Youngs during part of 
1940 and 1941. The excavator had a 2-cu.yd. bucket. 

Hook and Ladder mine at Smiths Flat, sec. 10, T. 10 N., R. 11 E., is 
held by Charles Fossetti, Smiths Flat. Lindgren ^ has published a map 
showing the underground channels of this region and states that they 
are inter-rhyolitic but have yielded several million dollars by drifting. 
Bert Bryan of Smiths Flat worked a channel on this property known 
as the Gray Lead channel until 1932. An old shaft 114 feet deep was 
available at a point 350 feet gouth of the State highway. He sank an 
additional 38 feet, ran 330 feet south in bedrock, and raised to the chan- 
nel, which he worked for a length of 1,150 feet. He states that gravel 

1 Logan, C. A., Mineral resources of El Dorado County : California Jour. Mines and 
Geology, vol. 34, 206-280, 363-365, map, 1938. 

2 Lindgren, op. cit., U.S. Geol. Survey Prof. Paper 73. p. 173. 



2.')() PLACF.R MINIXf; FOR GOLD IN CAMFOKNIA [Bull. 135 

Avas 70 feet wide ami 1 \ to 3.\ foot deop at this point, and tliat 10 IVet back 
from tlic face a sample i-an $1 !•..')() per enbie yard from a 2-foot depth of 
{jravel with jrold at $20.67 i)er ounce. He was workinjr down-stream 
(southward), and a drop of 11 feet in 50 feet of ehainiei made furtlier 
work too ditlKeult. He thinks that several hundred feet of this channel 
remain in place, but that it is cut off by the Deep Blue Lead channel. 
Workinjjs have been surveyed and mapped by Andrew Xesbit of Hanimon 
Enj;ineering Company. 

Horseshoe Bar. W. I). luf^ram, (Jridley, operated a drajjline 
dred<ie on this bar on Middle Fork American Kiver just below Michipran 
Bluff durinj; part of lf)41. Dredpfinj-' was done in Placer County also, 
as the river passes throu<>h the property, and the center of the river 
is the county line. 

Horseshoe Dredging Conipcniy, Youujrs, operated a drajxline dredge 
on the Frank Kipp property during part of 1940. 

W. 1). Ingram, F'oresthill, operated dragline-dredging e(piipment 
on the following properties in 1941 : Craig Osborne, Craig Koyce, Craig 
Salt Water, Emma J. Hodgkin, and Red Raven. (See Hor.seshoe Bar 
al.so.) 

Irish Creek Mining Company, Georgetown, operated a nonfloating 
washing plant on the Morgan property during part of 1940. 

Lemroh Mining Company, 2401 Baysliore Boulevard, San Fran- 
cisco, operated a dragline dredge during part of 1940. 

Max and Jnnetion mine yielded 110 ounces of gold aiul 15 ounces 
of silver from 14,000 cubic yards of gravel in 1942. 

McQueen and Downing of Weaverville operated a dragline dredge 
on Carson Creek during part of 1940. 

Orlomo Company, Box 548, Placcrville, operated a dry-land dredge, 
using a dragline excavator with l2-cu.yd. bucket, on Indian Creek 
throughout ]!)41. 

Pafchen Property. Charles Patcheu, 80 Broadway, Placerville, 
holds 80 acres in sec." 18, T. 10 N., R. 9 E., M. D.. containing fmile 
of stream gravel 100 to ."{OO feet wide aiul 8 feet deep in Martell Ravine. 
He states that this pays by hand-work. 

River Pine Mining Company, 2432 l!)th Avenue, San Francisco, 
operated its drairline dredge on North Fork of Cosumnes River in sec. 
26, T. 9 N., R. 10 E., M. D., near Xashville, during the last half of 1941. 
The dredge was operated in Amador County during the first half of 
the year. 

Setter property yielded 548 ounces of gold aiuI 70 ouiu*es of silver 
from 77,500 cubic yards of gravel washed in 1942. 

.Sturbuck Property. Frank ^I. Starbuck of Rescue holds 120 acres 
in sec. 10, T. 10 X.. R. 9 E., M. D., which was worked by placer miners 
in the early days. Two to 6 feet of gravel are covered by feet of 
overburden. It is reworked from time to time in the rainy season and 
produ(!es a little gold. Part of the tract near the mouth of Sweetwater 
Creek was worked recently by a dragline dredge. Marcus Starbuck 
holds 40 acres in the adjoining section 17 that may pay by working 
with a dragline dredge. (}ravel is 250 feet wide and 10 to 15 feet deep. 
It was worked !)>• hand in the earl\- days. Bedrock is decomposed granite. 



Sec. IVJ MINKS HV COUNTIKS 257 

Tivo Clxiinul Mine. Tins is ;i consolidation ol' several old mines 
held bv W. S. Eaton, for whom E(\ (Jreen, IMaeerville, is aj^'ent. More 
than 'ioOO acres in sees. H, 10, 15, 22, 27, ;U, T. 13 N., K. 11 E., M. D., 
8 miles northeast of (Jeor^etown are included. A channel containing' 
white (juartz boulders, and another containinj;' cemented p^ravel and 
andesitic bonlders are iVmnd here. Both have been worked by hydraulic 
and drift minin?-. The cemented "-ravel was crushed in stamp mills. 
Driftinji' has been done for a distance of 2500 feet south from Otter 
Creek, which cuts the channels. According to Bert Bryan of Smiths 
Flat, 2 miles of cliannel remain unworked in the vicinity of Kentucky 
Fiat, lie was plannin*;- to prospect the ground in the summer of 1944. 
Descriptions of old workings are contained in the references given 
below under the names of Kates, Kenna, Kentucky Flat, Mississippi, 
Tiedemann and Two Channel. 

i:!ibl. : State Mineralogi.sfs Reports XII, pp. 114, 115, 117 ; XIII, p. 160 ; XV, p. 302 ; 
XXXIV, p. 2,'')1. 

Van Dyke, Modrell, and Warner, Box 822, lone, operated a drag- 
line dredge with a -l-cu.yd. bucket on the Emma Gordon property dur- 
ing part of 1941. 

Ventura mine of 90 acres in sec. 20, T. 10 N., R. 12 E., M. D., is 
owned by Ed ChrLstian, IMaeerville. A tunnel has been driven through 
a ridge containing a lava-capped channel ; 1300 feet of this on the 
Christian property connected with workings in adjoining property. 
Christian states that at least 80 acres of the property contains a gravel 
deposit but that little is known of the gold-content. The same channel 
mav exist in 100 acres held by F. H. Richardson of Placerville and in 
160 acres in sec. 24, T. 10 N., R. 11 E., held by Mrs. Hedwig Bitzer and 
Alma L. Howard, Smiths Flat. 

Widff Property. W. C. Wulif of Rescue holds 35 acres of placer 
ground, which produces gold by small-scale methods, in see. 8, T. 10 N., 
R. 9 E., M. D. The productive part is 30 to 36 inches deep. The gold 
has evidently come from eroded pockets in the immediate vicinit3\ 

FRESNO COUNTY 

Hopkins and Becker, 3231 Fernside boulevard, Alameda, operated 
a suction dredge invented by Becker on the San Joaquin River near 
Friant in 1941 and recovered 298 ounces of gold and 61 ounces of silver 
from 121,000 cubic yards of gravel. The dredge had a 6-inch centrifugal 
gravel pump, gasoline engine, and riffle tables mounted on a steel pontoon 
hull. The suction point could be lowered vertically 28 feet below water 
level. 

Grant-Service Rock Company recovered 114 ounces of gold and 16 
ounces of silver in preparing 339,955 tons of sand and gravel for con- 
crete aggregate in 1942. In 1943, recovery was 36 ounces of gold and 4 
ounces of silver in preparing 210,000 tons of sand gravel. 

Griffith Company and Bent Company, 418 South Pecan Street, Los 
Angeles, which supplied gravel for building the Friant dam in 1940, 
recovered 443 ounces of gold and 73 ounces of silver from 400,000 tons 
of gravel. In 1941, the recovery was 4,990 ounces of gold and 747 ounces 
of silver from 3,935,620 tons of sand and gravel. In 1942, recovery was 
205 ounces of gold a-nd 29 ounces of silver from 121,700 cubic yards of 
sand and gravel. 

17 



258 PLACER MINING FOR GOLD IX CALIFORNIA [BuU. 135 

Tinn Bar MiniiKj Corporation, lo'M Colley;e Avenue, Berkeley, 
operated a dredge on jirojierties of Grant Pacific Rock Company and 
V. Roulard in 1942. 

HUMBOLDT COUNTY 

The eastern part of Humboldt County contains plaeer «rravels on the 
Trinity and Klamath Kivers. A little prold is produced by small-scale 
methods from beach sand. A number of these operations and properties 
have been described in a recent rejjort of the State Mineralo<i:ist.^ The 
princii)al i)roducer in recent years has been the Peai-ch miiu* described 
below. 

Orick Placers, Inc., operated a washing plant in the CJold lilutf dis- 
trict in 1943 to recover gold from beach sand. 

Pcarch mine of 180 acres in sec. 32, T. 11 X., K. 6 E., II.. formerly 
owned by P. L. Young, (Orleans, has been sold to Roy McCJain, ()rleaiis, 
who is operating it (1940). The proi)erty is 1 mile northeast of Orleans 
on the dirt highway to Happy Camp. An old terrace of Klamatii River 
with bedrock about 50 feet higher tlian the present river contains a 
placer deposit 80 feet thick at the face of the present hydraulic pit. 
Only the lower part of the deposit is gravel with boulders of a maxinuim 
diameter of 18 inches. Overlying this is a great thickness of fine over- 
burden and soil. The slate and chloritic schi.st bedrock dips steeply in 
several directions. 

During the water-sea.son the mine is kept in operation for 24 hours 
per day by a crew of 10 men. A mile and one-half of Hume from Pearch 
and Cheney Creeks has a capacity of 1,300 miner's inches with a head 
of 225 feet at the mine. Three giants are set up, one with G-inch nozzle- 
opening, the other two with 5-inch openings. They are supplied with 
water by means of 840 feet of 36-incli and 30-incli pipe, 900 feet of 20- 
inch pipe, and 2,800 feet of 15-inch pipe. Gold is recovered by means of 
wood-block riffles in a 'Y' sluice reaching both ends of the pit and di.s- 
charging to Klamath River. To reach the river from one end of the pit, 
192 boxes, each 12 feet long, are required. The 'Y' branch to reach 
the other end of the pit contains f)4 boxes. (Jrade is half an inch per 
foot. .McCJain estimates that he miiu's 1,000 cubic yards per day during 
a working-season of 5 to (i months. Water wheels furnish power for 
compressed air aiul electric lights. 

Production for 1939 is given by the U. S. Bureau of jNIines - as 
follows: "Cleaning bedrock at the Pearch hydraulic mine on the Kla- 
math River northeast of Orleans yielded 154 ounces of gold and 23 ounces 
of silver." Figures on production for 1940 are not available, but in 
1941 the mine produced 266 ounces of gold and 38 ounces of silver from 
128,500 cubic yards of gravel. 

Bibl. : State Mineralogisfs Keport.s XI\-, p. 4114 ; XXI, p. :n5. 

' Averill, C. V., Mineral re.sources of Humboldt County : California- Jour. Mines and 
Geology, vol. 37, pp. 4y!»-r>28, iy41. 

"Merrill, C. W., and (Jaylord, H. M., Cold, .silver, copper, lead, and zinc in Cali- 
fornia: U. S. Bur. Mines, Minerals Yearboolt lOSfl, p. 2:{3, 1940. 



MINKS UY rorxTiF.s 




3. S2. rearc-h mine, Huiiil)<>l(lt County. Photo hy coin-tesi/ of Hoy MiGai 
rrpr'tnleil jroni Caliloriiiii Jonnidl of Minrs <inil (IroU.ffti, October l'>'il, p. 513. 



IMPERIAL COUNTY 

The placer pold produetiou of Imperial County has been small in 
recent years. The followinj; notes are extracts from a recent report by 
Sampson and Tucker/ contained in the California Journal of Mines 
and Geolojj-y for A^wil 1942. The same issue contains a few notes on 
gold placers by Ilenshaw.- 

Gold Delia placer mines are in sec. 20, T. 13 S., R. 19 E., S.B., 9 
miles east of Glamis, and are owned by Cold Deltas Corporation, C. R. 
Zappone, president, 1001 Subway Terminal Building, Los Angeles. 

Placer gravels in washes of present water courses from the Chocolate 
Mountains have been developed by a shaft sunk 300 feet through uncon- 
solidated gravel to bedrock. Cuts and shafts indicate a body of gravel 
2 miles long and half a mile wide. A 6-f()ot thickness of gravel at the 
bott(mi of the 300-foot shaft is said to contain $0.50 to $2.00 per cubic yard 
in gold. 

Picacho Basin mine (Placer). The basin consists of low, rolling 
hills covered in part by washed gravel and detritus from the neighboring 
hills. These superficial deposits are gold-bearing and have been washed 
by ^Mexicans for years and recently, by dry Avashing machines. The 
gravels have been worked along the arroyo between the Picacho lode mine 
and the old village at Picacho. It is reported that the gold-bearing 
gravels have an average value of 35 cents per cubic yard. These gravel 
deposits are 25 miles north of Yuma. Idle. 

IMbl. : State Mineralogi.sfs Report XXII, p. 200 ; Hull. 92, p. 15G. 

1 Samp.son, R. J., and Tucker, W. 15., Mineral re.'iource.'^ of Imperial County : Cali- 
fornia .Jour. Mines and Geolojjy, vol. "S, pp. 10.';-145, l'J42. 

-Henshaw, Paul C, C.eology and mineral deposits of the Cargo Muchacho Moun- 
tains, Imperial County, California: California Jour. Mines and Geology, vol. 38, p. 190, 
1942. 



260 i'LA(i;k minin(; kok com) ix cArJFOKNiA [Bull. l:>."> 

Potholes (IMacor). These dry phan-rs ;iie lociitcil 10 miles iiortiieast 
of Yuma, Arizona, and several miles west of liafruna Dam; elevation 
150 feet. Tlie {jold-bearin}; <;ravels of this i-e<iion were extensively worked 
in the early days by Indians and Mexicans and are now worked out. 
Value of the {jold produced from the Potholes placers is reported to have 
been $2,000,000. 

Hlbl. : State MineraloRisfs Hepnrls XIF, p. 242; Mil, p. :! H ; XXII, p. 2t;i ; IJnll. 
92. p. LIS. 

KERN COUNTY 

Holcoinh Valley Placer Company, lessee of the Monarch Rand mine 
in the Randsburj,;: district, prodiiced <>old in 104.'^ a.s a byproduct of a 
])lacer operation carried on primarily for scheelite. (Iravel was delivered 
by a carry-all to a stationary washing plant. 

Monarch Rand Mininfj Com])any opei-ated a dry-land dred^^e in the 
Randsburp: district intermittently during (5 months of ]942 for the 
recovery of sciieelite and gold. 

Placer Concentrators produced gold in 1948 as a byproduct from 
a placer sdieelite operation on the Patsy and Victory Xo. 2 mines in the 
Randsburg district. 

Hand Cold Dredging Associates, Russ Building, San Francisco, 
installed a connected-bucket-type dredge with eighty-two 3-cu.ft. buckets 
to work the Tungold mine 1] miles noi-thwest of ]»andsburg in 1942. 
Tlie dredge was moved from Shasta County, wliere it liad been ojierated 
by Roaring River Dredging Company. It was reconstructed, and jigs 
were added in order to recover .scheelite as well as gold. ()i)erations 
started on November 1, 1942, and continued until June 10, 1948. when 
the dredge capsized. It wa.s righted later in the year as described by 
Macaulay.^ 

LOS ANGELES COUNTY 

Ciold was discovered in Los Angeles County in 1884, and the placers 
of San Franci.squito, Placerita, Casteca, and Santa F'elicia canyons were 
worked between the years 1884 and 1888 by the ])riests of San Fer- 
nando and San Buenaventura Missions. The placers of San (iabriel 
Canyon were worked by the i)riests of San (Jabriel Mission and also by 
the native Californians until the discovery of gold in northern Cali- 
fornia by Mai-sliall in 1848 at Sutter's mill.- In i-ecent years jiroduction 
of jilacer gold in this count\' has been small. Two pi'oducers of sand 
and gravel for the construction indu.stry reported the recovery of small 
amount.s of placer gold from llie San (iabiiel district in 1948. 

' Mac-aulii.v, W. I!., HiKlitinj; cap.'^i/.i-tl dridR.- takes .">0 miiiute.s: Rng. and Min. 
Jour., April l!t44. 

- Tinker. W. H., ami .'-■aiiipsun, R. .1.. iUiieral re.snurces of I^os Anpeles Coiint.v : 
('allfornia .lour. .Miiie.s and Ceolony, vol. ;i;{. pp. 17:1-270. l!t:!7. 

Hrartle.v, W. W.. California mineral pro.lnetion. 1!t24: ("alifornia Min. l^ur.. Hull. 
!ir.. p. 47. I!t2.^.. 



See. IV] MINES 15Y COUNTIES 2(51 

MADERA COUNTY 

H. A. Berg, Box 581, Madera, operated a .suction dredf^e on the 
P're.sno River in the Dennis district in 1041, and recovered 257 ounces of 
gold and 74 ounces of silver from 22,000 cubic yards of prravel. 

Cassanrang Ranch. Two suction drcdsjjcs were operated on this 
ranch in the Dennis district wheiv the Fresno Kiver passes throuf^h it, 
in 1941. Operators were E. J. (Jibbons and Richard A. Cassauran<,'. 
Madera. 

G. E. Nohlc d' Sons operated a suction di-ed<i:e on the .1. T. Pierce 
ranch in the Potter Kidge district during nearly all of 1942. Recovery 
from 7790 cubic yards of gravel was 118 ounces of gold and 35 ounces of 
silver. 

Polk Ranch. Suction-dredge operations on this ranch in the Potter 
Ridgfe district produced 148 ounces of gold and 82 ounces of silver from 
9000 cubic yards of gravel in 1942. 

MARIPOSA COUNTY 

Although small placers yielded many millit)ns of dollars to early 
miners in Mariposa County, the rich Tertiary channels found in counties 
farther north are lacking because the protective blanket of lavas and 
other volcanic ejecta did not extend this far south. ^ Hence the placers 
of Mariposa are now less important than those of other counties along 
the Mother Lode. Short descriptions of the many lode-gold mines of 
this countv are contained in State Mineralogist's Reports XXIV and 
XXXI.2 

Barker Corporation, Hornitos, operated a dragline dredge on Eldo- 
rado Creek 1 mile from Hornitos in 1940. In 1941, operations were 
continued here and on the following other pro])erties: Givens, Trabncco, 
Turner, and Waltz in the Hunter Valley district, and the Adams, 
Explorers, Inc., Munn, Penrose, R. AVilliams and Stratton in the Mother 
Lode district. In 1942 there were 22,000 cubic yards of gravel washed 
at the Kehoe property, Avhich yielded 112 ounces of gold and 32 ounces 
of silver; 109,000 cubic yards Avashed at the J. Lord i>roperty yielded 
833 ounces pf gold and 229 ounces of silver ; and 16-3,500 cubic yards 
washed at the Trabncco property yielded 1016 ounces of gold and 280 
ounces of silver. 

Thurman and Wright, 960 Russ Building, San Francisco, operated 
a dragline dredge with 4J- and 6-cu.yd. buckets on property of the 
Crocker-Huffman Land and AVater Co. during the last half of 1941. 
Operations Avere continued on Burns Creek during part of 1942. 

1 Julihn, C. E., and Horton, F. M., Mineral indu.stries of the United States: Cali- 
fornia, Mines of the southern Mother Lode region Part II, Tuolumne and Mariposa 
Counties: U.S. Bur. Mines Bull. 424, pp. 1-179, I'.MO. 

- Laizure, C. McK., current mining activities in the San Francisco district with 
special reference to gold: California .Jour. Mines and Oeolfigy, vol. 31, pp. 27-4*!, l!)3ri. 

Laizure, C. McK., Mariposa County: California l)i\-. Mines, Mining in California, 
State Mineralogist's Rept. 24, pp. 79-122, 1'J2S. 



262 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

Trchor Corporation, Box 51, Mariposa, with Robert D. Mueller in 
charge, operated a draprline dredg:e with 2-cu.ft. bucket on the Chase 
Ranch in the Hunter Valley district in 1940. Earlier operations were 
conducted at Mormon Bar and A*rua Fria Creek. In W41, operations 
were conducted on the followin}; properties: Fretz, Gaskill, Machado, 
Trabucco, Turner, and Waltz. In 1942, operations for 8J months on 
the C. C. Pierce property pn Corbett Creek yielded 289 ounces of ^o\d 
and 57 ounces of silver from 100,000 cubic yards of }?ravel. 

MERCED COUNtY 

P. H. Bottoms, Box 121, Merced Falls, operated a draj^line dredge 
with 2-cu. yd. bucket in the Snellinj; district during? part of 1940. 

Merced Dredging Company, 1805 Mills Tower, San Francisco, 
operated an electric connected-bucket dredn:e with sixty 10-cu.ft. buckets 
half a mile south of Snellinfr in 1940, 1941, and part of 1942. 

Sayi Joaquin Mining Company, 1805 Mills Tower, San Francisco, 
operated a connected-bucket dred<rc with sixty-four 10-cu.ft. buckets 3 
miles west of Snelling in 1940, 1941, and part'of 1942. 

Snclling Gold Dredging Company of Snellinjr operated tw^o electric 
connected-bucket dredges on the Merced River between Merced Falls 
and Snelling: throughout 1940 and 1941, and during part of 1942. The 
property is in sees. 10, 11, 12, T. 5 S., R. 14 E., M. D., and covers a 
deposit of uiicemental gravel and sand 10 to 20 feet deep with bedrock 
of volcanic asli. One of the dredges has seventy-two and the other 
sixty-six 7-cu.ft. buckets. Otherwise the dredges are much alike with 
steel hulls 42 by 96 feet and the usual riffle system. 

Thurman and Wright, 960 Russ Building, San Francisco, operated 
a dragline dredge with a 6-cu.yd bucket on land of Crocker-Huffman 
Land and Water Company, in 1941. This operation was partly in Mari- 
posa County and partly in Merced County. 

Yuha Consolidated Gold Fields, 351 California Street. San Fran- 
cisco, operated a connected-bucket dredge with seventy-two 9-cu.ft. 
buckets 4 miles cast of Snelling in 1940 aiul part of 1941, in T. 5 S., 
R. 15 E., M. 1). The dredge and part of the property were taken over 
from La (I range Gold Dredging Company in 19.{0. Gravel ranged in 
depth from 18 to 36 feet, and bedrock is slate near Merced Falls but is 
volcanic ash on the lower part of the tract. A little platinum was recov- 
ered with the gold. 



Sec. IV] MINES BY COUNTIES 263 

NEVADA COUNTY 

Some of the larpjest known reserves of placer gravels in California 
are in Nevada County. Long stretches of Tertiary river channels that 
were formerly the sites of great hydraulic mines remain nnworked as 
a result of the injunction-decision of Judge L. B. Sawyer in 1884 against 
North Bloomfield Mining Company restraining that company from dis- 
charging debris into the streams. Federal legislation passed in 1893, 
called the Caminetti Act, created the California Debris Commission. 
This act is printed in full in the appendix of this report. For large 
hydraulic mines on the Sacramento-San Joaquin drainage, tailing must 
be restrained by dams. The Upper Narrows dam on the Yuba River was 
built for this purpose and was completed in 1939, but only a little 
hydraulic mining has been done above it to date (1945). One reason 
for this was Limitation Order L-208 of the War Production Board, which 
shut down nearlv all the gold mines, remaining in effect from October 
8, 1942 to July i, 1945. 

Estimates of yardages available for hydraulic mining above this 
and other dams have been made by Jarman ^ and Bradley.- A few 
recent operations have been described in a report by Logan ^ and older 
ones in a report by MacBoyle,^ but MacBoyle's report is out of print. 

Calaveras Gold Dredging Company operated a dragline dredge at 
Steep Hollow^ in the You Bet district from April 8 to August 20, 1940. 

Clerkin pi'operty consists of 156 acres of patented land in sec. 24, 
T. 17 N., R. 7 E., M.D., near French Corral, owned by W. P. Clerkin 
of French Corral. Clerkin states the ground contains 30 to 40 acres of 
gold-bearing gravel, of which a 60- to 70-foot depth contains practically 
no gold. From 8 feet to 10 feet at the bottom is blue gravel, and the last 
foot contains most of the gold. Clerkin thinks that this deposit repre- 
sents a high bench of the old Eocene channel about 100 feet wide and 
adjoins the bedrock tunnel claim of the French Corral placer. Clerkin 
works the property for about 2 months in the spring of each year with 
750 miner's inches of water that flows from Bloody Run Creek from 
melting snow. 

Dakin Company, 917 Sacramento Street, San Francisco, operated 
a dragline dredge at Champion Flat along Deer Creek from January 1 
to March 1, 1940. The excavator was equipped with a li-cu.yd. bucket. 

Esperance. See French Corral. 

French Corral placer is a property of 1,700 acres in sees. 23, 24, 25, 
35, T. 17 N., R. 7 E., M. D., including the Kate Hayes, Esperance, Fra.ser 
and Alexander, Bedrock Tunnel, and Milton placer mines, owned by G. M. 
Standifer, Balfour Building, San Francisco. The property contains 
approximately 1 mile of unworked length of the Eocene channel worked 
by hydraulic methods at North Bloomfield, North Columbia, Badger 
Hill, American Hill, North San Juan, Sweetland, Birchville, and French 
Corral. 



1 Jarman, Arthur, An investigation of "the feasibility of any plan or plans whereby 
hydraulic mining operations can be resumed in this state" : California Min. Bur., Mining 
in California, State Mineralogists Rept. 23, pp. 54-116, 1927. 

- Bradley, W. "SV., Dams for hydraulic mining: California Jour. Mines and Geology, 
vol. 31, pp. 345-367, 1935. 

3 Logan, C. A., Mineral resources of Nevada County, gold placer mining: Cali- 
fornia Jour. Mines and Geology, vol. 37, pp. 431-436, 1941. 

♦ MacBoyle, Errol, Mines and mineral resources of Nevada County: California 
Min. Bur., State Mineralogist's Rept. 16, pp. 91-108, 1919. 



264 I'LAIKK MINING KOK (H)IA) IN CALIFOHNIA [Bull. 135 

In November, 1040 a report was made on this property by L. A. 
Smith, uho sank some shafts to sample the frravel and who had the 
results of some drillinjr that had been done about 1938. The foUowinj; 
is abstracted from Smith's report : About one-third of a mile of channel 
on this property has been |>artly worked by the hydraulic method, and 
the resulting; excavation is kmtwn as the Esperance pit. An averajre of 
about 65 feet of the top jiravcl has been i)iped off of an area rou<rlil>- 600 
by 1.500 feet. The bottom jrravcl remaininji- on bedrock measures rou<rhly 
200 yards wide by 500 yards lon^i' by 12 yards dee]). Gold content of 
this 1.200,000 cubic yards should be hiohcr than the channel averagre, 
and the deposit can be worked mechanically. Smith's sampling results 
in this bedrock g^ravel area turned out as follows: 

Shaft No. 1 121.4 ft. OO.Tc' p.'i- cii.vd. B<Mlr..cU 
Shaft Xo. 2 :U.r. ft. 41.0c per cu.yd. Bt'drock 
Shaft No. 4 24.5 ft. 3G.0<* per cu.yd. Bedrock 

Average of the aiiove bedrock shafts — 45.1^ 
Shaft No. 3 S.O ft. 23.C<' per cu.yd. Xo bedrock 

Avera>;e of the above four shafts — 13. Ic' 
Cut No. 1 30.0 ft. 3G.0(^ per cu.yd. No bedrock 

(Extends above collar of shaft No. 1) 

Cut No. 2 5.0 ft. 45.0'' per cu.yd. No bedrock 

(E.xtends above collar of shaft No. 3) 

Average value of all cuts and shafts — 41.4(f per cu.yd. 

The gravel that was sampled was tough and tuicemented in general, 
but it contained lenses of cemented gravel. It was washed through a 
trommel 4 feet long and 14 feet of sluice box. Smith estimates that 70 
to 90 percent of the gold was recovered. lie thought that a moderate 
amount of scrubbing in a large trommel would insure a good recovery 
of the gold. 

The un.stripped ground north of the p]sperance pit was drilled 
about 1938 with the results given below. This work was done as explora- 
tory work and all holes are therefore not in the channel. The lines were 
roughly 1,200 feet apart, and the number "2" was not used. 

Line No. 1 has three holes in the channel — holes No. 7, No. 9, and 
No. 10. The average depth is 89 feet and average value 21.1 cents per 
cubic yard. The width of channel is about 600 feet. 

Line No. 3 has four holes in the channel — holes No. 6, No. 7, No. 8 
and No. 9. Using holes No. 7, No. 8 and No. 9, Smith figured a 500-foot 
width with average depth of 56 feet and average value of 14 cents per 
cubic yard. 

Line No. 4 is made up of three very poor holes, the deepest of which 
(128 feet) did not reach bedrock. The channel at Line 4 is evidently 
comparatively narrow for an unknown distance or until it widens again in 
the Birchville pit. 

The Line 1 drill holes appear to confirm the shaft samples in the 
shallow ground. Smith as.sumed 30 feet of 40-cent bottom gravel at 
Line 1, and 59 feet of 12-cent top gravel overlying it and thus arrived 
at the 89 feet of 2 1.1 -cent gravel shown by the drill holes. 

Line 3 drill holes do not stand up to the average indicated by Smith's 
shaft results. Thirty feet of 40-cent bottom gravel at Line 3 would 
show a 21 -cent average for the 56-foot average depth without assuming 
any values in the top 26 feet. 



Sec. IV] MINES BY COUNTIES 265 

Before these drill hole results are accepted, Smith believed they 
should be checked by sinking two or more shafts over selected, drill holes. 
He did not sample the upper or overburden gravels, but pan tests that 
he made would indicate a value in the neighborhood of the recoveries 
reported by Schroder and others who hydraulicked top gravel from the 
Esperanee pit. These reported recoveries run from 10 to 17 cents, old 
price, or an average of probably 20 cents per cubic yard at present price 
of gold. This figure is confirmed to some extent by one sample taken 
near his shaft No. 1. This sample began at approximately 30 feet above 
bedrock and extended to approximately 60 feet above bedrock, with an 
average gold content of 36 cents per cubic yard for the 30-foot sample. 

Smith proposed to work by mechanical methods the gravel already 
stripped in the Esperanee pit, about 1,200,000 cubic yards, then to pros- 
pect the unstripped ground and strip by the most feasible means, either 
mechanical methods or hydraulicking. He expected this work to expose 
an additional 2,400,000 cubic yards of gravel of a grade that would show 
a profit if worked by mechanical methods. In the fall of 1945, such a 
project had not yet been started. 

Water for this property is obtained from Shady Creek, and is 
brought into the Pine Grove reservoir by means of a 4-mile ditch. The 
original capacity of the reservoir was 300 acre-feet. Applications have 
been made for 53 second-feet or 2,120 miner's inches of water. 

GrcenJioni Dredging Company operated a dragline dredge at 
Quaker Hill in the You Bet district from January 1 to December 31, 
1940, using an excavator equipped with a 2-cu.yd. bucket. 

Hall and French. See French Corral. 

A. B. Innis of Nevada City operated a dragline dredge equipped 
with a 14-cu.yd. bucket at the Malakoff mine from October 16 to Decem- 
ber 31, 1941. The yield from 72,000 cubic yards of gravel was 333 
oun'ces of gold and 33 ounces of silver. The operation was continued 
in 1942 and the yield from 146,000 cubic j^ards of gravel was 694 
ounces of gold and 64 ounces of silver. 

Kate Hayes. See French Corral. 

Kanfield and McKhiley of Lincoln, operated a non-floating washing 
plant on the Parker Ranch from June 27 until September 13, 1940. 
Kaufield and Danison of Nevada City operated a dragline dredge on 
Columbia Hill near North Bloomfield from March 1 to April 20, 1941. 

M. K. Gibson Mining Company, Grass Valley, operated a dragline 
dredge on the Elder, Martel, Neirzert, and Thomas properties in 1941. 

Milton. See French Corral. 

Omega mine is in Sec. 16, 17, T. 17 N., R. 11 E., M. D., 3 miles 
southeast of the town of Washington. It is owned by South Yuba 
Mining and Development Company, Charles A. Kaas, secretary-manager, 
420 Market Street, San Francisco. The last mining was done in the 
season 1941-42, ending in the summer of 1942, by Omega Company, of 
which Jack Little was manager. 

A new 30-inch pipe line has been installed to take water directly 
from the ditch, giving a pressure of 175 pounds per square inch. 
The old pipe line from reservoirs is also a 30-inch line, but it gives 
only 90 pounds per square inch pressure. Three resei'voirs hold about 
35 acre-feet of Avater. The company takes 5000 miner 's inches of water 



2(jt) i'LA(i:r{ MIXING von cold ix California [13u1I. l^o 

Iroiu tlu' Si)utli Fork (»f the Yuba Ivivei- under old water-rijrlits. Tliis 
amount is usually available to about the niidtlle of July, then the amount 
^Tadually deelines. The nuiin ditch system is 12 miles ion«r and starts 
just below Lake Spauldiujr. ()u«'-third of this 12 miles is flume 4 feet 
by () feet, ineludinji- 4 miles at the stai-t. The flume was i-epaired with 
1200 M board feet of lumbei- in 1!>41. A lower ditch system, i)art of 
which is 'i- by 4-foot fhime, picks uj) water from various canyons to 
feed the reservoii's with 1200 minei-'s inches of water. It is 7 miles lon^'. 
Other e(|ui]>ment includes a camp to house 7") men, and a sawmill with 
a capacity of l(i M to 20 ^I board i'cot of lumber pei- day operated by 
steam ])()wcr. It includes two (iO-inch saws, a foui--saw edjier, and a 
cutolf saw. Lumber is ])roduce{l only for the use of the mininjr company. 

(!()ld is recovered in a sluice 3 feet wide, ',i\ feet deep, aiul .\ mile 
loup', erpiipped Avith cross rifHes of .'{0-pound and 4r)-p()und steel rails. 
'IMie jrrade is 6 inches in KJ feet. Duty of the water is about :{ cubic 
yards jier miner's inch ])er day. l^edrock is a slaty schist. 

Accordiujr to Theodore T^arscMi of Nevada City, who was super- 
intendent of the last operations, the coni])any holds about .'{000 acres 
of land containin-;' 2:),0()0.000 to ;U).()()(),000 cubic yards of jrravel. The 
face of the pit is carried (iOO feet wide and loO to 18.") feet hi^h in an 
Eocene chaniuM I.IOO feet wide. 

The ()me<:a ('()mi)any bepan hydraulickin<i' .March 0. 1!»41. utili/.iufr 
storajie sj^ace for tailiniz' in the recently completed I'pper Narrows 
Debris Dam at Smai-tsville. Duriuti' the season the comjiany washed 
42f>.()."{7 cubic yards of jzravel, which yielded l."{02 ounces of »>()ld and 
4f) ounces of silver. In ]f)42 the mine was operated by Omejra Com- 
l)any, and lessees from January 17 to July 7. The yield from 818,17.') 
cubic yards of jrravel was 1740 oiuices of <rold and r)4 ounces of silver. 
Tn 1043 bedi-ock was cleaned, yieldin<r (54 ounces of jiold and 2 ounces 
of silver. 

Pilot DicdijiiKj Comixiiifj, {'ottouwo(Hl, operated intermitteutl\' in 
1!)40 on the C'olebui-n ))roi)ei-t\- with a drajiline dredge. 

Ihlief urn Mine. See Western (lold, Iiie. 

William Hichtcr tO Sons oj)erated a dra-iline dredj-e at Sct)tts Flat 
from .January 1 to October 13, 1!)4(). Tn i;)41 this firm operated a dra<4- 
line tlredjie on the Donnellx' and Johnson property. 

Sun J nan (iold Company, F. Ti. ]\Iorris, president, ]\Ionadnock 
Buildin^i", San Francisco, liolds 5484 acres of ])atented mininjr claims 
on San Juan Kid;:e principallv in the followiu<r sections: Sec. 3(). T. 18 
N., 1?. 8 E.; Sec. 1, T. 17 N.. K. 8 E. ; Sees. 1, 2. 4, .'). (i, 7, 8. !), 11, 12. 
T. 17 N., K. fi E.; Sees. 3.1, 3(j, T. 18 N., K. !> E. ; Sees. 1(1. 21. 22. 31. 
T. 18 N., It. lOE., M. D. 

These holdinjis include the famous MalakolT hydraulic mine form- 
erly operated by North Bloomfield .Mining Company. Accoi-din<r to 
officials of the i)resent company, this old i-ompauy recovered .$2,830,000 
during' the period from 1870 to Februaiy 1884 from ^n-avel that yielded 
12 and a fraction cents ])er cubic yard with «rold at $20. ()7 |>er ounce. 

In tlie vieinity of North Columbia is a i)art of the same channel 
that has been stripped by old hydiaidic mininjr to a dejith of abont 
150 feet. Gravel still remains in this i)art of the channel to a deptli of 
about 300 feet. ]\raps in the ])o.ssession of F. L. ^Morris sliow that this 
has been drilled to determine the yold content for a distance of 2), miles, 



Sec. IV] MINES BY COUNTIES 267 




Fig. S3. Badser Hill property of San Juan Gold Company. 

on the Central, Consolidated, and Western placer mines. Rows of holes 
about 500 feet apart -were drilled across the channel, and the distance 
between the holes is about 200 feet. Morris states that this sampling 
has indicated a gold content considerably higher than the recovery men- 
tioned above for 100,0000,000 cubic yards in a strip down the center of 
the channel 600 feet in width. As bectrock was reached in only small 
areas of the old workings, gravel remaining in this stripped part of the 
channel should be better than the average gravel already mined because 
of the concentration of gold on bedrock. 

Application for new water-rights has been made as follows : Hum- 
bug Creek, 20 cubic feet per second; Spring Creek, 15 cubic feet per 
second ; Grizzly Canyon, 25 cubic feet per second ; Bloody Run, 50 
cubic feet per second ; Middle Fork of Yuba, 300 cubic feet per second. 
Rights are held on Wolf Creek for 25 cubic feet per second and on 
Malakoff pit for 5 cubic feet per second. Old ditches are being retained 
and may be reconditioned to handle all w^ater except that of the Middle 
Fork of Yuba River. Estimates have been made on the cost of a new 
system for this water of $800,000 for flume and dam only or $1,540,000 
total for the entire system complete to the mine. This includes 22 miles 
of flume and 2 miles of ditch. 

As the cost of installing this water-system is high, owners of the 
property are considering the installation of mechanical methods of 
mining instead of hydraulicking. If mechanical mining is used, storage 
of tailing on the property may prove feasible. 

A. B. Innis operated a dragline dredge with a 1 |-cu.yd. bucket at 
the Malakoff mine from October 16 to December 31, "1941. The yield 
from 72,000 cubic yards of gravel was 333 ounces of gold and 33 ounces 
of silver. In 1942, the yield from 146,000 cubic yards w^as 694 ounces 
of gold and 64 ounces of silver. 

Western Gold Incorporated operated the Relief Hill mine by the 
hydraulic method in 1941 and was one of the first companies to utilize 
debris storage behind the Upper Narrows Dam on the Yuba River. W. 
H. Taylor, 942 Russ Building, San Francisco, is president ; and Claude 
E. Clark, Graniteville Star Route, Nevada City, is manager. The mine 
is 3 miles east of North Bloomfield in sees. 4, 9, T. 17 N., R. 10 E., M. D. 



268 



1'I;A(1:K MININd VOH (i(>I,l) IN CAIJIOUNIA |r.llll. 1 •"..") 




I-'ic. SI. W.-st.-i-n I ;. 



J'liul,, l,ji lli.nnns F. I.\mh 



Janiiair"' estimated that (i.OOO.OOO eubie yii\\\s of .travel have already 
been washed at this mine and that r),()U(),()()() to l.l.OOOjHH) eid)ie yard's 
■were still available, lie stated that owners estimated that .'{(),()()().()()() 
enbic yards were available at that time. Present ownei-s estimate a 
still liijrher yardajie available. Drift mining; lias been dcnie at this 
property as well as hydraulic niininj>'. Dnrintr the war the mine has 
not been in operation because of shorta«re of labor and Limitation Order 
L-208 of the "War Production ]5oard. The operators are planninjr to 
open up the mine for hydi-aulickinji on a lar^^e scale when labor and 
materials are available. 

The following deso-iption of an carlici- ])criod of o])ei-ation at thi.s 
min^ is fi-om Gardner and Johnson:''' The Relief Hill Mininji- Company 
bejran operations near ('am|)tonville in the antunui of lU'M and worked 
4 months in lfi;32 before tlie water supply failed. An old mine was 
bein<r rejuvenated; the }rravel was 200 feet thick. About .lOO miner's 
inches of water was used durinp: the season. A total of ]0()() inches will 
be used when the mine is fully reopened. The old pit Avas cleaned and 
vir«rin {jravel reached in 1!):^2 just as the water played out. Tailin«rs 
were imjiounded behind dams in a dry canyon. The ditch line is 7 
miles lon<r. The pipe line is 14 to 22 inclies in diameter, and the effective 
head is 210 feet. The sluice boxes are 48 inches wide; riffles are wooden 
blocks. A duty of ,'} cubic yards ))er 24 hours ]>er miner's inch is 
expected. A crew of 15 men worked 120 days in 1932. 

Wifdndnttc Dndcjincj Compaiwj, Box 228, Nevada City, operated a 
dragline dredge, using a 2J-cu.yd. bucket on the Perrin and Pingree 
Ranches from October 18 until December 31, 1940. The yield from 



^ Jarman, Arthur, op. cit.. p. 11 1. 
"Gardner, K. 1^., and Johnson. ('. M., 
Pari II, Hydraulic-kinR, oti-. : l.'.S. IJnr. Miii. 



inhiR in the we.stern T'nited .Sii 
<•. t;TS7. p. ,52, 11134. 



Sec. IV] MINES HV COUXTIKS 260 

H7,()()() cubic yanl.s (A yravel was 771 (nmccs of jiold and lOf) ounces of 
silver. The company also operated a draj-line dredpe on property of 
the Alpha Stores in" the You Bet district durin«r 1940. In 1941 this 
company did further work on the Perrin and Pinfzree properties. The 
yield from 1 :?().()()() cubic yards of firavel washed at the Perrin property 
was 118() ounces of <rold and 155 ounces of silver; the yield from 70,000 
cubic yards washed at the Pinp:ree property was :VA9 ounces of jrold and 
58 ounces of silver. 

You Bet )iii)U's include many of the old hydraulic mines famous in 
the early days of that method of minino-, such as the followinor : Palmyra, 
Newark, Arkansas and Greenhorn, Starr, Red Dofr, Missouri Canyon, 
Gail Placer. Rose and Duryea, Emigrant, Smith and Powell, Chicken 
Point, Atkins and Taylor, You Bet, Brown Bros., Washington, Browns 
Kill, Niece and "West, Birds Eye Canyon, Poverty, and Walloupa. The 
group includes 1150 acres of patented land and 120 acres of locations in 
sees. 25, 35, .36, T. 16 N., R. 9 E. ; sees. 29, 80, 31, 32, T. 16 N., R. 10 E. ; 
sees. 2, 11. 14. 15, T. 15 N., R. 9 E. ; sec. 6. T. 15 N.. R. 10 E.. M. D. ; also 
151 acres of timberland in sec. 28, T. 16 N., R. 10 E. ; also the following 
ditches: a 12-mile English ditch Avith the fir.st right on 1500 miner's 
inches from Steep Hollow Creek; a 5-mile Star ditch on the south fork 
of Greenhorn Creek with the second right to 500 miner's inches of water, 
and 13/21 interest in the Irish ditch with the second water right on Steep 
Hollow Creek. This property is now owned by Alpha Stores, Ltd., Fred 
F. Cassidy, president, Nevada City, California. 

Immense yardages of gravel were washed at these properties by the 
hydraulic metliod in the early days from one of the great Tertiary river 
channels, but large yardages still remain unworked. The Jarman'' 
report of 1927 quotes p. A. Goodale as estimating that the property 
still contains 12,000,000 to 24,000.000 cubic yards of gravel containing 
enough gold to pay for hydraulic mining. Tom Brady, who lives at 
You Bet and who holds the adjoining Jupiter group of 100 acres in sec. 
31. T. 16 N.. R. 10 E., states that a part of the channel starting at a 
point east of You Bet and running northward has never been worked, 
except a little on the surface. Brady says that the best content of gold 
is found where the bedrock starts to rise on the west side of the channel 
and that this has not yet been mined in this particular section of the 
channel. 

The following quotation is from the Colfax folio by Waldemar 
Lindgren :^ 

"At Red Dot; .nml Iliiwkins Ciinyttii, ncnr Yon Bet, the deep frravel has aRain 
l)een exi)(>sed and is heyoiid doubt ooiitimious between the two points. The gravel 
here is similar to that at QuaUer Hill. The deepest jyavel has been hydraulicked only 
in the jilaces mentioned bnt considerable drifting by means of tunnels and inclines 
has l>een done from Niece and West's claims for H miles northeast on the Steep 
Hollow side. The channel has very little fall, the average elevation being 2620 feet. 
It is estimatetl 47,000,000 yards have l)een removed, leaving over 100,000,000 yards 
available. Much of this would be ditHcult to wash on account of lack of grade. 
Ueports of yield and grade of gravel are not available but the You Bet diggings have 
probably produced .$.3,000,000." 



' Jarman, Arthur, op. cit., pp. 44-116. 

*> l.,indsren, Waldemar, U.S. Geol. Survey Oeol. Atlas, Colfax folio (no. G6), p. 9, 
1000. 



270 IT.ACI'.U MININ'C FOR COI,!) IN ( AMIOUMA [ Illll I. 1 o") 

V(»ii r»«'t Milling ('(»iu|);iii\- did sonic liydriiiilic iiiiiiiii^r on lliis prop- 
erty in the winter of l!»i;M4' jilter bniltlin- ;i dclnis diun ;ind jrcttin^r 
a permit tVoni tlic ('alirofiiiji Debris Comniission. \Voi-k Wiis stopped 
ill l!n4 by a court injunction on tbe ground that the water below the 
dam was rendered unfit for (h)mestic |)urposes on account f)f its turbidity. 
In im.") many of the claims were leased to (Miincsc niineis, who did some 
drift niiniu;r that is rejjorted to have been xcry product i\t'. Apparently 
the last hydraulic mining' was done under the supervision of .). \V. Scott 
about IICM. He used :{,()()() miner's inches of water under a 2S()-foot 
head and recovered ^^old in a sluice tiia-t had a slope of 7 inches to 12 
feet. Hydraulic minin«: was done on the Ked Doj: property with a bank 
200 feet hijrli. and at tlie lirown's Hill property near the town of Vou liet 
with a bank 2.")2 feet hi^h. He was al)le to remove riiii-<j:ravel without 
blastiu}; at the rate of (i.OOO cubic yards per 24 hours or 2 eul)ic \ar(ls per 
miner's incli per day. Some of tlie bottom <irouiid recpiired blastin<r and 
was moved at the i-ate of 10,000 cubic yards j)er day or '^f^ cubic \ards 
per miner's im-h per da\', yieldin^r .")! cents per cubic yard, accoidinjr 
to his rei>ort. 

Mining cost was 7] cents ])er cubic yard, and stoi-a<;e in the Combie 
Ileservoir of the Nevada Irrijration District cost M cents jier cubic yard. 
Tailing:- from the Red Doij ]iro])erty was discharfxed to (Jreenhorn Creek 
tliroujih a tunnel tluit starts 70 feet above the creek and is 22 feet down 
in the bedrock at the mine. Pipe lines in use duriiiLr this period of opera- 
tion included one line 7()o feet lonjr of j^ipc 2(), 20, IS, and 15 inches in 
diameter. A second pipe line contained I,:}")!) feet of the same sizes of 
l)ipe. Nozzles used on the jriants were 7 inches and (> inches in diameter 
at the outlet. Because of difficulties with nuiddied water and conse- 
quent law-suits brou<;ht by Pacific (las & Electric Comjiany, coupled with 
the fact that the Nevada Irri<;ation District needs the remaining' sjiace 
in the C'ondjie Reservoir for tlie storage of water, it is doubtful that any 
further storaj;e of liydraulic tailing will be sold in this reservoir. How- 
ever, some consideration has been <;iven to raisin<i- this dam to provide 
additioiud space for the storage of hydraulic taiiiiif:-. 

In H)40 the Wyandotte I)redj,Mn<r C'ompan\-, the San Carlos (iold 
Dredjrinjr Company, and the Pilot l)red«:in<r Com])any operated di-aj:line 
di-ed<res to handle tailin*; from former hydraulic operations on (Ireen- 
liorn Creek. In 1945 tiie property was beinjr operated under a lease 
and option lield by I*hil P. Fredericks, Manx llotel, San Francisco. 



Sec. IV] MINES BY COUXTIES 271 

PLACER COUNTY 

IMaiiy important old placer luines are located at Dutch Flat, Gold 
Run. ]\Iiclii<ran Bhiff, Forest Hill, and other places in Placer County. 
Descriptions of many of them were published by Logan ^ ip the Cali- 
fornia -Journal of Mines and Geolop-y for January, 1936. This publica- 
tion contains a lono; table of placer mines with references to older reports 
on them, and the reader is referred to that table for references to litera- 
tin-e on the older operations. The famous drift-mines of the Forest Hill 
Divide were described by Koss E. Browne - in State Mineralogist's Report 
X, for ]89(), and a good map and vertical sections accompanied the report. 
It is out of print but may be consulted in many libraries. 

Below are a few notes on recent operations and on a few properties 
that are believed to contain reserves of possible commercial grade. 

H.J. Aalders and W. W. Fraihcr of Lincoln operated a dragline 
dredge using a l|-cu.yd. bucket on the Gladding Ranch 4i miles north 
of Lincoln from January 1 to July 15, 19-40. 

C. N. Chittenden of Lincoln operated a non-floating washing plant 
on the Rizzi Ranch from January 1 to July 20, 1940, and moved it to 
the Mulligan Ranch on August 1 where operations were continued until 
the end of 1940. The yield from 75,000 cubic yards of gravel was 222 
ounces of gold and 45 ounces of silver, and from 26,000 cubic yards of 
gravel was 132 ounces of gold and 31 ounces of silver from the respective 
properties. In 1941 Chittenden operated a non-floating washing plant 
on the Johnson Ranch in the Lincoln district. Gravel was delivered by 
dragline excavator with a f-cu.yd. bucket. The yield from 43,500 cubic 
yards of gravel was 282 ounces of gold and 51 ounces of silver. 

Duffy property, in sec. 3, T. 13 N., R. 11 E., and sec. 24, T. 13 N., 
R. 9 E., ]\r.D., and intermediate sections, is held by George L. Duffy of 
Forest Hill. Duffy states that he controls about 18 miles of mineral 
rights on the ^Middle Fork of American River either by options on 
patented ground or by special-use permits from U. S. Forest Service 
and the Federal Power Commission. The holdings are for a proposed 
dredging project and extend from the original Ruck-a-Chucky dam site 
to the mouth of the Rubicon River. The gravel has been sampled for 
a distance of 1^ miles from a point near the mouth of Volcano Canyon 
near the line between sec. 5 and sec. 6, T. 13 N., R. 11 E. and going down 
stream. Casing 11 inches in diameter was sunk at intervals of 100 to 
250 feet. The holes were staggered, alternate ones being on opposite 
sides of the river: The depth ranged from 20 to 25 feet, and DufTy 
states that the average value in gold was 60 cents per cubic yard with 
gold figured at $35.00 per ounce. Width of the gravel is 350 to 400 feet. 
Eight miles at the lower end of the holding were sampled by means of 
sinking 70 caissons, 5 feet in diameter, by hand. Many of these did not 
reach bedrock, as it was possible to sink them to a depth of only 15 to 
16 feet. Gravel was washed in a sluice and long tom, and according to 
Duffy gave a return of 32 cents per cubic yard. Gravel ig 500 to 700 
feet wide on this lower end of the holding. Duffy states that early work 

1 Logan, C. A., Gold mines of Placer County : California Jour. Mines and Geology, 
vol. 32, pp. 49-96, 1936. 

2 Browne, Ross E., Tlie ancient river beds of the Forest Hill Divide: California 
Min. Bur., State Mineralogist's Kept. 10, pp. 435-405, I8I1O. 



272 I'LA( Kit MIXINf; FOR GOLD IN CALIFORNIA [I>nll.l3r) 

Oil the bars and in the rivor \vas done in circiilai- \u\s. Tlic pits wcri- 
kept unwatered, and the jrravel was reiiM)ved by means of hydraulie ele- 
vators. Mueh of the j^ravel between these eircnhir pits was not distnrbed 
b.y this early method of mininj:. 

A part of Dntfy's holdinjrs known as Horseshoe Bar in sees. 4, 5, T. 
1:^ X., R. 11 E., was worked by AV. D. Inp:ram of Gridley with a draj^iine 
dredge in 1041 and 1942. The wasliin<r plant was desij^ned to serve a 
5-cu.yd. dragline excavator, bnt the one aetnally in use was a Northwest 
drapfiine with a 2-eu.yd. bucket. Results from this operation are said 
to have been f?ood, but it was shut down by Limitation Order L-208 of 
the War I^roduction Board in 1942. 

El Oro T)rcd(iinr) Coinpany of Colfax operated a drajjline dredjre 
on Indian Canyon in the Iowa Hill district from February 4 to September 
19, 1940. A second dred^'e was operated in Sliirttail Canyon from Au^'ust 

6 until October 31, 1940. 

Gold Placers, Inc., 320 Capital National Bank Buildin*,'. Sacramento, 
operated a drayline dredjze on the Robinson Ranch in the Ophir district 
from April 30 to Aufiust 30, 1941, and on the Leak Ranch from September 

7 to December 20, 1941. 

Gold Recoveries Corporation, Box 58, Auburn, operated a dragline 
dredge on the William Ayers and Anderson property in the Ophir dis- 
trict during 1941. 

Hallstrom and Lindblad, Route 7, Box 4343A, Sacramento, operated 
a non-floating washing i)lant, to which gravel was delivered by a dragline 
excavator with a l|-cu.yd. bucket, in the Ophir district during 1940. 
The yield at the liaker Ranch 6 miles east of Koseville from 124,000 cubic 
yards of gravel was 355 ounces of gold and 9 ounces of silver. The 
yield at property of the Placer Realty Corporation from 165,000 cubic 
yards of gravel was 471 ounces of gold and 30 ounces of silver. This firm 
continued operations in 1941 on the Joseph ^looney, ]\Iathilda Bahr, 
and Rogers Ranches and in Miners Ravine, all in the Ophir district. 

W. 1). Ingram (see Duffy property also), Box 225, Foresthill, oper- 
ated a dragline dredge on Horseshoe Bar on the county line between 
El Dorado County and Placer County during 1941. 

Innis Dredging Company, Nevada City, operated a dragline dredge 
on Dry Creek from January 1 to June 1, 1940. 

Jasper-Stacg Com pang (Recalp Company) of Lincoln worked out 
its ground in Auburn Ravine 2 miles east of Lincoln in May 1940. A 
dragline excavator with a 2-cu.yd. bucket was used. 

Kaujield and McKinlcy, Box 274, Lincoln, operated a non-floating 
washing plant, using a mechanical excavator, on the liove Ranch in the 
Ophir district fr(»m February 20 to June 2H, 1940. 

La Kamp Bros, of Dutch Flat operated a non-floating washing plant 
at the Mutual mine in the Dutch Flat district during 1941. (1 ravel was 
delivered with a bulldozer. 

Lebanon Consolidated Mines, 200 Bush Street, San Francisco, 
worked the Occidental drift mine in the Iowa Hill district from January 
1 to December 31, 1941. The yield from 3766 cubic yards of gravel was 
536 ounces of gold and 63 ounces of silver. 



Sec. IV] MINES BY COUNTIES 27o 

Lost Camp mine is a hydraulic mine of 440 acres 2 niileK by road 
from Blue Cauyon, at an elevation of 4:W() feet, iu sees. 22, 23, T. 1(5 N., 
R. 11 E., M. D. The t'hanuel contains interbedded layers of soft 
rhyolite tuff and fi-ee-washin^ Avhite (juartz gravel. Work on the prop- 
erty has proceeded at intervals over a lonjz period by three different 
methods, jjround sluicing, hydraidickin<r, and drifting. Several million 
cubic yards of gravel probably renuiin unworked, but little is known 
about the gold content. 

The present owner is the Robie Estate, Wendell T. Robie, manager. 
Auburn, California, but the most recent work was done by a California 
corporation called Lost Camp Mining Company from 1934 to December 
1941. The property includes water rights on ^Monumental and Fulda 
Creeks. 

In 1944 a case was pending in the Sacramento Superior Court (No. 
60474, Department 4). involviiig a complaint of Carmichael Irrigation 
District about muddy water discharged with tlie tailing from this mine. 
Stipulations limited the hydraulic season to the period from November 
15 to April 30 of each year. This was a temporary arrangement which 
may be modified later. In this case McGeachin Placer Gold Mining 
Company and Mayflower Gravel Mining Company contend that the 
United States Debris Commission is a party in interest, because the tail- 
ing is impounded by a debris dam on the North Fork of the American 
River, and that the case should be tried in a Federal court. 

In an entirely different suit in tlie Superior Court at Auburn, Lost 
Camp Mining Company was ousted from the property and the title 
confirmed to the Robie Estate. This suit involved a claim by the Cali- 
fornia Debris Commission of $4009.30 for tailing storage by the debris 
dam, but the Superior Court at Auburn excluded this point from the 
decision. 

Mayflower Gravel Mining Conipa)ty, care of Richard Detert, ^Vlills 
Tower, San Francisco, holds a very large mining property at Foresthill 
now containing 5800 acres in sees. i5. 22, 23. 24, 25, 26, T. 14 N., R. 10 E., 
and including the following mining claims: Texas, Sacramento. Wash- 
ington, Garland Mill Slope, Excelsior, Hope, T^ncle Sam, Green Spring, 
Live Oak, Small Hope, New Jersey (mineral rights). Brushy Slide, 
Dardanelles, Oro, and Adams pit. 

The mine was first worked by hydraulicking. Tjater it was an 
important drift mine, working the .same channel as the bottom lead in 
the adjoining Paragon property. The priincipal production, about 
$1,600,000, was made between 1888 and 1899. The cemented gravel was 
crushed in a 20-stamp mill of 850-pound stamps, dropping ]()() tinies per 
minute. The battery screen was an iron plate punched with holes 0.2- 
inch in diameter, and the capacity was 6 J tons per .stamp-day. The gold 
was recovered by amalgamation. John Hays Hammond^ quotes the 
following figures: From December 11, 1888, to September 24, 1889, a 
total of 33,787 tons of gravel was mined from a length of 1620 feet of 
channel and yielded on crushing .$272,616.50 or $8.06 a ton. 

The Mayflower operators worked downstream on the bottom oi- 
main lead to the boundarv of the Garland ^lill Slope claim (tlien under 

''Hammond, John Hay.s, The auriferous gravels of ralifornia : California .Min. 
Bur., State Mineralogist's Rept. 9, p. 120, 1890. 



274 I'LACKK MINIXC KOK liOl-D 1\ fALU'ORNIA [Bull.135 

otluM- owiu'i'sliip), iis well as upst rcaiii lo tlu' Para^DU line. Tlio May- 
HowtM- <i:rt)uii(l contains an uiiworked souincnt of \>\<x Uhio Load 1 .\ miles 
Ion? inc'liidinji- tlioso inirts in tlio Excelsior and (larland .Mill Slope 
claims. Tlie bedrock tunnel of the ^layflower has been diiven ahead 
but must be driven an additional loOO feet to connect ■with the Ivxcelsior- 
Haltimore bedi'ock tunnel. When this connection is made the H-mile 
segment of channel Avill be drained. Water has been too troublesome in 
the i)ast. 

Old re])orts desci'ibe an U])i)ei' lead in this same clianiiel which was 
worked in tiie i'ara^on mine. (Jeorjie DntVy of Forest hill did about a 
mile of drifting in several directions in the Mayllower shaft, 1")() feet 
above bedrock, about ]{);}8. His gravel averaged $.{..")() per ton with 
gold at .ji.'M i)er ounce. The south drift was the best and yielded $(> to ^1 
per ton from cemented gravel. Nuggets of ^1 to $!..')() were found. 

He al.so did some i)raspeetiug in the old hydraulic-bank near the 
collar of the ^laytlower shaft by sinking five shafts ri.l feet apart, eacli 
about 20 feet dee]). The.se shafts represent the lower 20 feet of a !K)-foot 
depth of gravel and gave returns of $4..')() i)er cubic yard, according to 
Dutfy. He believes that this 90-foot depth could be dredged, liedrock 
is rhyolitic tutf". A segment of the Orono inter-volcanic channel. 2 miles 
long, extending from Mayflower bedi-ock tuniu>l southwai-d is supi)o.sed 
to exist in thi.s property. 

Recent work has been done in the hydiaulic pit at Smith's Point 
and the Albright claim (sec. 27) ou a bank 4.")() feet high. A 22-mile 
ditch from Shirttail Canyon will carry aOOO miner's inches of water 
giving a head of r)2.> feet. Only 82.") feet of head has been used recentl.w 
A giant supi)lied by a 15-inch pipe uses 7- and it-inch nozzles. 

McGeuchin Placer Gold Mining Conipanij has extensive holdings 
of placer gravel in sees. 2, 8, 4, 10, T. 14 X., K. 10 E.. M. 1).. near Iowa 
Hill. Several of these have been described by Logan"* under the names 
McGeachin Placer (Jold Mining Company, Morning Star drift mine, 
and Long Point Mining Company (Jupiter). C. H. Dunn, Sacramento, 
is president; 1. E. Rose, Iowa Hill, is maiuigei-. The pi-operty includes 
1700 acres, (iround suitable for liydraulic mining is known as the 
Rig Dipper, which iiu'ludes the old Irish and Ryi'iie and Horman claims. 
Other claims include the Jupiter, Hazelroth. Schwab, Weber, and 
Winchester. 

Water supi)l\ is obtained from Xorth Fork of Shirttail .Canyon 
and includes three ditches aiul the i\Iorniug Star reservoir 10 miles 
from the mine, which holds ISOO acre-feet. The main or McKee ditch 
carries li.jOO miner's inclies, and would furnish 400 feet of head at the 
mine if a 24()r)-foot penstock of Mi- and ;U-inth pipe were built. This 
ditch heads in .sec. 27\ T. 15 X.. R. 10 E. The Morninu- Star ditdi heads 
in sec. 18. T. 15 X., R. 11 E. 

In connection with ])lans that were being made to resume hydraulic 
mining, a report was made in December li).'iS by F. II. Reynolds and 
Company. Consulting Engiiu'ei's, Saci-amento, and samples were taken 
by I. E. Ro.se. Sampling was done in old hydi-aulic banks roughly 
50 feet in height aiul consisted of cuts 2 feet wide and 1 foot deej). 
Four of the sami)les were usetl in making calculations of gold-content. 
and a fifth was discarded because it had been taken near bedrock, and 

• I.oBan, C. A., op. cit., 193G. 



See. IV] 



MINKS BY COT^NTIKS 



275 




Fio. 85. Sampling: hydraulir liaiik r>() tVt-t lii^h 
(^ompany. Phola bii (nitrtisii 



tlie gold-content was lii<rli. Ko.se tliinks tluil 1 he i^iduiul contains 'i.l.OOO.- 
000 to 30,000,000 enbie yards of «rravel witlx.nt oveihnrdcn tliat will 
yield 20 cents per enbic yard in gold, in a i-onglily circular area :i")()0 
feet long and more than 2{)()() feet wide. Additional >ai-dage is avail- 
able with overburden. Kose states that !..')( )().()()() cubic .vai-ds have 
already been worked on the Irish and l>yrue claim, and .l.OOO.OOO lit 
().000,600 cubic yards on the Ilorman. JJanks range from 40 1o 2^^.') 
feet in height. Kose states that drifting oi)erations cai-ried on for 
2 years recently yielded gravel miming from M'^ to ■^\) per cubic yard 
in gold. 

H. ^y . McKinehj of Newcastle operated a dragliue ili-edge ou the 
Fisher Ranch in the Ophir district from -lune 17 to .Iul\- :'>1. 1!I41. 

Midland Company, Inc., Box 8. Sawyers IJar, moved its dragline 
dredge from the Lincoln district to the North Fork of Salmon River 
in Siskiyou County during 1940. The dragline exeavatoi- had a 1 j-cn.yd. 
bucket. 

Panoh Gold Dredging Coinjxnn/. IJox SiKi. Liucohi. opeiated two 
dry-land outfits on the Forsyth and J^ewis and (i. E. Stoll ]n-oi)prties 



270 I'LACKK MtNlNC lOU COM) 1\ CAr.IKOKNIA | 1 >lll I. 1 n.') 

«liiriii;r 1!»40. Kroiii M;ir«-li to Octohcr HUl this conipaiiy oiu'i-atcd 
a nou-floatiii^^ wasliiiijr plant on tli.' Fci-i-ari property in tlie Opiiir 
district, (iravcl was delivered l»y a dca-j-Iiiie excavator with a 11-cn.yd. 
biieket to a washing- i)lant ecpiipped witli Ainlay howls. The opera- 
tion at the Korsyth and Lewis property was continned dnrin^r 1!)41. 

Pautlc Bros, of Lincoln operated a dry-land placer machine eciuip- 
jx'd with fonr Aiiday bowls on the Ahart. Ferreva, and Kaneko Uanches 
in the Ijincoln district duriny; 1!)4(). The yield from ]7i),8()() cnbic yards 
of «rravel was ():{2 onnces of jrold and 111 onnces of silver. The ^rravel 
was delivered with a 1-cn.yd. drajrline excavator. 

I'amijun inliu, in sees.. l:{, 18, 19, :{0, 31, T. 14 N., K. 11 K., and 
.sec. 24, T. 14 X., K. 10 E., M. D., is one of tlie large hydranlic mines 
of the Forest Hill distriet 2 miles from Foresthill at a i)laee formerly 
called Hath. Lo«ian '' published two pajres of description of this mine 
in State Mineralo-iist 's Report XXXIl., and that descrii)tion is up to 
date with a few exceptions, as follows: I'arajion Mines. Inc., W. K. 
Wilson, president, Foresthill, has acciuired the lease and option form- 
erly held by Alanta Mines, inc.. of which Kiiij: (I. (Jillette was i)resi- 
dent. The property now contains 17()() acres owned by the .1. F. Thomp- 
.son Estate, of which Charles II. Sejrerstrom, Sonora, is administrator. 
Wilson states that an old tunnel that was driven through the hydraulic 
bank to carry the water-ditch contaijied leaks that probably helped to 
eau.se a serious cave at the jiro])erty in 1 !):{'>. He has abandoned this 
tunnel and moved the forebay and ju])e-lines to the ea.st side of pit. 

Rosci'illc Gold l)r(<hjiu(j Compuiiy, Mol California Street, San Fran- 
cisco, operated a dredge in Strap Ravine (i miles east of Koseville from 
January 2:} to the end of lf»40. The dredge was driven by electric 
powei' and had a bucketline of seventy-two .'{-cu.ft. buckets. This opera- 
tion was continued during ]f>41. 

IStewart Grarcl Mines, c/o -I. I). Stewart, LJS Conunercial Street, 
Aubui'ii. controls al)out ;{()()() aeies on the great Eocene river chanmd 
that pas.ses through Dutch I'Mat and (lold Kun. The |)r()perty is in sees. 
2, :i, 4, !), 10, T. IT) X.. K. 10 E.. M.I)., and covers a length along the 
channel of 2 miles. 

It is consj)icuous because highway no. 40, the main route from Cali- 
fornia to Truckee and Reno, runs for a mile at the base of one of the 
old hydraulic baidis nearly 200 feet high. The main line of the Southern 
Pacific Railroad is at the top of this old hydraulic face. The channel is 
li mile.s wide at thi.s point and the gravel was origiiuilly oOO feet deep 
in the middle of the channel, .so a depth of several hundred feet remains 
unvvorked. According to Stewart, a length of 11, ")()() feet south of the 
highway has not been drifted on bedrock. 

The mine is provided with a 4000- foot bedrock tunnel in green- 
stone, which reijuii-es no timbering. The p<irtal of this is 17) feet higher in 
elevation than Canyon Creek, and this ci-eek empties into Xorth Fork 
of American River. The tunnel is driven on a grade of three-(|uarters 
of an inch per foot, and during hydraulicking operations it was provided 
with a sluice and steel rails for riffles to recover the gold. Tailing was 
discharged to C'anyon Cieek. 

•■• Logan, C. A., op. tit. 



Sec. IV] MINKS BY COUNTIES 277 

The south end of the property for a lenjith of about half a mile and 
width in the bottom of 400 to 1200 feet has been worked to bedrock by 
means of hydraulic mining. The lower 60 to 80 feet of the gravel is 
cemented and required blastiji? in advance of hydraulickinp:. After 
hydraulic mining ceased the property was worked by drifting and a 
tunnel was driven 1800 feet on the bedrock beyond the 4000-foot tunnel, 
which is at a lower elevation, to give access for drift-mining. Logan " 
has published details on production during short periods from 1872 to 
1879 in State Mineralogist's Report XXXII. 

To the north of the railroad, on the part of the channel that drains 
toward Bear River, are many millions of cubic yards of unworked gravel 
in the Dutch Flat district. Extensive deposits in this area are owned 
by James L. Gould, Soda Springs P. O., Placer County, and Nichols 
Estate Company, c/o Arthur Nichols, 846 Mendocino Avenue, Berkeley. 
Individual menibers of the Nichols family hold tracts in this vicinity also. 

Volcano Miyiing Company, Ltd., 1018 Mills Building, San Francisco, 
worked the Volcano drift mine in sees. 18, 19, 20, T. 14 N., R. 11 E., M.D. 
between Foresthill and Michigan Bluflf in 1940. The operation was 
continued in 1941, and 4000 tons of gravel yielded 206 ounces of gold 
and 27 ounces of silver. 

PLUMAS COUNTY 

Tlie mineral resources of Plumas County were described in the 
California Journal of Mines and Geology ^ for April, 1937, which con- 
tains a geologic map of the county showing the locations of the principal 
mines and a long table of mines giving references to earlier reports. 
Placer mining was not active in the county in 1937, and only a few 
such mines are described. Descriptions of many of the old drift and 
hydraulic mines are contained in the chapter on Plumas County ^ of 
State Mineralogist's Report XVI. which is still available at this time 
(1945). A map showing drift and hydraulic mines of La Porte district 
is on file at the San Francisco office of this division. 

Baker amd McCowan, Box 305, Chico, moved a dragline dredge from 
Butte County to Meadow Valley in the Quincy district and operated from 
August to December, 1940 and during 1941. The dragline excavator 
had a 1^-cu.yd. bucket. 

Innis Dredging Companjf of Nevada City moved its dragline dredge 
from Nevada County to Lights Creek in the Lights Canyon district and 
resumed operations August 4, 1940. The dragline excavator had a 
2-cu.yd. bucket. In 1941 this operation was continued from elanuary 1 
to September 22, and the yield from 250,000 cubic yards of gravel was 
1653 ounces of gold and 130 ounces of silver. 

Lohicassa Company, Box 812, Sacramento, operated a dragline 
dredge on Jamison Creek in the Johnsville district from August 20 to 
December 24, 1941. 



" Logan, C. A., (Jold niine.s of Placer County, tJold Kun di.strict : California Jour. 
Mines and Geology, vol. 32, pp. 62, 63. 

See also : Dutch Flat District, pp. 56-58. 

^ Averill, C. V., Mineral resources of Plumas County : California Jour. Mines and 
Geology, vol. 33, pp. 79-143, 1937. 

* MacBoyle, Errol, Mines and mineral resources of Plumas County : California 
Min. Bur., State Mineralogists Rept. 16, p. 188. 1920. 



278 I'LACKK MININO FOR (SOLD IN CALIFORNIA [Bull. 135 

SACRAMENTO COUNTY 
Natomas Company 

Natomas Company. Fonmi I^nildinjir, Sacramento, ^vas the larfjest 
prodncer of placet- ^'old in Calif oi'iiia in both 1!U() and 1!)41. Durin<r 
those years the company operated seven (lri'd<res in the Folsom district. 
Operations wci-e cnrtailed in 1!>42, lf)4.S, and 1!)44, hut were heinj; 
iiici-eased a<j:ain in the summer of 1!)4"). One of tlie dred<res is e(iuipi)ed 
with buckets holdiiifr 17 cubic feet each, two with 16-cu.ft. buckets, 
three with 12-cu.ft. buckets, and one with 9-cu.ft. buckets. The dejith 
whicli they can difj beh)w the surface of the water ranjxes from 80 feet 
to 70 feet. Bedrock is volcanic ash. More <;ravel e.xists below the vol- 
canic ash in parts of tlie dred<rinjr field, but it is not jrold-bearing. 
Thomas McC'ormack of Rio Vista is ])resident, and R. O. Smith of Nato- 
mas i.s fjeneral mana<rer of jrold dred<;injj:. This company desi<rns and 
builds its own dredges, and the following: notes on recent practices have 
been supplied by R. G. Smith: 

Mdin Drirc. Tiie main drive of the bucket line has been diaufred 
to direct current (d-c) motors witli Ward-Leonard controls. Tiie drive 
is throujjh reduction <;ears wliich are entirely enclosed in cases. The 
reason for this is the moi-e efficieiit variable speed and the j?reater ea.se 
of control. Because of this, the company has been able to increase 
bucket-line speeds as much as 50 jiercent where the {gravel is not too 
hard. To supply the dii-ect current a motor prenerator set is installed 
in the bottom of tiie hull. Many of the controls for other machinery ai-e 
installed in the same room. This helps to maintain the center of frravity 
of the drediie at a low ])oint. Other new drives for main bucket line, 
used by different companies consist of two-motor alternatiiif; curi-ent 
drives with either constant or variable speeds tln-ou<rh \'-belt di-ives to 
the main drive shaft ; also a sin<:le two-speed motor drive through V-belts 
to the sinji:le main drive shaft of the ohl-type conventional drive. 

Ladder Hoist. AVhere motors have been installed for tii(> main drive, 
it has become necessary to have a separate ladder hoist. The.se are driven 
throujjh enclosed fzears and are jrenerally ojKM-ated with i-e«i;enerative 
brakiii^. The hoist is e(piipped Avith ma<j:netic brakes and post or <;ravity 
brakes operated i)ne»nnatically ; also with T;illy over-speed and over-haul 
control. Greatly increased hoistinj? speed has been adoj^ted. 

Swing Winch. Where motor generator .sets have been installed for 
d-e main drives, individual bow-liiu' winches driven by d-c motors have 
been installed. They are driven throu«;h enclosed reduction fiears and 
are equi})ped with AVard-Leonard controls. This j^ives efficient variable 
speed and maximum <'ase of contr-ol foi- thi' side-swiufjr. Line ti-avel on 
both sides of the dred<:e is made the same. N'ariations of (his pi'actice 
have consisted of usinj; a-c drive a.s hei-etofore, i.s()]alin«i- the bow-line 
drums to operate without fioiufr thi-on^ih a chain of jrears on the side-line 
winch. The side-line winch is used as drive for one bow-line and a 
separate winch and motor are used for the other bow-line. Most of 
these installations are ecjuipped with pneumatic control for both sliifting 
of frictions and for brakes. Brakes are usually of the f;ravity type, 
which are released by the i)re.ssnre of com]ire.s.sed air. 

Side-Line Wineli. Pneumatic control of both brakes and frictions 
has become frencial i)ractice, and the winches are driven by enclosed 



Sec. I\'J Ml\i:s 15V coiXTiKS 279 




reduction ^ciirs. Tlie use of i)iieun]atic control for tlie winches has done 
nway witli the j-reat inimber of operatinji- levers Avhicli formerly had to 
he placed to one side of the bucket-line. Now the winch room can be 
placed on tlie loupitudinal center-line of the dredjze, and this jrives the 
operator a much better chance to see Avhat he is doinpr. Pneumatic con- 
trol reduces the manual effort i"e<juired of the operator to a minimum. 

Screen Di'tn . Screens are now driyen either directly throu<rh 
ciu-losed reduction ^carina' set in the same line with screen or with V-belt 
drive with motor set on a horizontal plane. 

(loUl Savinfj. The tendency has been to increase the total width of 
.i:()l<l-savin<i' devices per cubic yard handled rather than to increase the 
total area. The total width of riffle-tables has been divided into nar- 
rower sluices, and this tends to increase the effective riffle area. The 
reason is that a tiltinji of the di-edjie in the lonjiitudinal direction giving 
a fore and aft pitch, tends to thi-ow all the fluid in the sluices to one side 
of the sluices. If the sluice is kept narrow, this tilting is not likely to 
expose the riffles on the high side of the sluice. Xatomas Company ha.s 
used jigs on some of its dredges since 1914. Where a jig 42 inches wide 
is used, the riffle sluices are made 21 inches wide. This is in contrast to 
a 8()-inch width formerly used. On the Natomas dredges on Avhich jigs 
are n.sed only a launder is placed between the distributor box beneath 
the screen and the jig, that is, no riffles are u.sed ahead of the jig. The 
niain consideration for the use of jigs is that the gold is difficult to 
anuilgamate. Two of the dredges of Xatomas Company are not equipped 
with jigs because the gold which they recover is not tarnished. Jigs may 
be able to save fine gold a little better than riffle sluices as ordinarily 
handled. Xatomas uses both Bendelari and Pan-American^ jigs. On 
the Boulelari jig the agitation is effected by an eccentric which actuates 
a circular rubber diaphram in the hutch. On the Pan-American jig the 
whole bottom of the jig is moved up and down by an eccentric, and the 
joint between the .stationary and the moving part of the hutch is a 
circular rubber part shaped like a tire-casing. Jigs need a thicker pulp 
than riffles. Too much water will carry the gold past the jigs. Hence 
only the high-pressure water goes over the jigs, and an equal amount 

1 Made by I'an-Anierlcun Engineering Company, S20 Park r Street, Berkeley, 
California. 



280 PLACER MININ(1 FOR OOLD IN CALIFORNIA [Bull. 135 

of low-pressure water is added below the jifrs. On a dredge handling 
500 to 600 fubic yards per hour, of which 40 percent goes to the gold- 
saving devices. (iOOO gallons per minute of high-pressure water is used 
and HOOO gallons per minute of low-pressure water. An arrangement 
that is (piitc connnon is to use a single-ceil jig as a rougher, with riffle 
sluices below the jig to take the overflow and to serve as emergency gold- 
saving e(juipment. The concentrates are amalgamated on riffles and 
then put over a cleaner jig, from which final concentrates flow to a 
ball-mill for .scouring the rusty gold. A variation consists of some riffle 
tables ahead of the jig.s and also of amalgamation of the jig concentrate 
in a continuous barrel amalgamator. Another arrangement consists of 
two-cell jigs with no riffles on the jig overflow. Concentrates are either 
subjecteil to riffle amalgamation or fed directly to cleaner jigs. The 
final pr()d\ict is then amalgamated. 

Hull Construction. Although some of the recently -built dredges 
have been e(|uipped with the conventional riveted steel hull, the tendency 
toward wcltled construction has been evident. Pontoon-type hulls have 
met with considerable favor even for dredges of 9 cubic feet and under, 
and for digging to depths up to 70 feet. The pontoons are of welded 
con.st ruction and are bolted together during assembly in the field. Hulls 
with welded construction have been in service for several years without 
any evidence of failure. 

Buckets. Rivetless bucket lips have been coming into greater favor 
rapidly. Perfection of small construction details and the operating 
advantages gained have been contributing factors to popularity. Low 
lij)s tiiat are welded to the bucket are coming into use in some places, 
but not yet in California. 

R. G. Smith points out that a dredge should be tailor-made to fit the 
particular tract of ground that is to be worked. The design of the 
dredge must take into consideration each of the following: 

1. Depth of the gravel. 

2. Whether the gravel is tight or loose. 

3. Whether large boulders are present. 

4. Whether there is a high percentage of sand and silt. 

5. Length of time that the dredge is expected to last. 

On one Natomas dredge the fines from the riffle sluices go to a sump 
containing a revolving sand-wheel. Buckets around the circumference 
of this wheel pick up the sand from the sump and discharge it to the 
same stacker that carries the oversize from the trommel. Silt overflows 
from the first sump to a second sump, where it is picked up by a purap 
and discharged through a pipeline that runs along the side of the stacker. 

Other Operators 

Capital Dredging Company, 351 California Street, San Francisco, 
operated two connected-bucket dredges on its property 5 miles south of 
Folsom throughout 1940. 1941, and until October 15, 1942. One dredge 
had 88 and the other 100 buckets of 18-cu.ft. capacity. They were both 
electrically driven. 

Carson Creek l)rc(l</in<j Company, 21(i Pine Street, San Francisco, 
wa.shed gravel on the Martin Quinn Estate from September 11 until the 
end of 1940, using a dragline excavator with a IJ-eu.yd. bucket. The 



Sec. IV] MINES BY COUNTIES 281 

operation was continuecl from Jaimary 1 until February 5, 1941, and 
was then taken over by Northwest Development Company. 

Climax Dredging Company of Folsom operated a dragline dredge on 
the J. Vincent property in the Folsom district from January 1 to April 
8,1941. 

Cosunincs Gold Dredging Company, 351 California Street, San 
Francisco, operated a connected-bucket dredge in the Cosumnes River 
district, 7 miles southwest of Sloughhouse during 1940, 1941, and until 
October 20, 1942. The dredge is equipped with 63 buckets of 12-cu.ft. 
capacity, and is electrically driven. 

Cutter and Mueller recovered gold as a by-product in the operation 
of a commercial sand and gravel plant at Fair Oaks in 1942. The 
recovery from 40,320 cubic yards of gravel was 183 ounces of gold and 15 
ounces of silver. 

General Dredging Corporation of Natoma or 811 W. 7th Street, Los 
Angeles, operated a dragline dredge on the American River in the Folsom 
district during nearly all of 1940. This corporation was dissolved Sep- 
tember 30, 1941, but continued to operate as General Dredging Company, 
a partnership. Dredge no. 1, equipped with a dragline excavator having 
a 5-cu.yd. bucket, was operated on American River. Dredge no. 2, oper- 
ating on the ancient river channel in the same district, used a dragline 
excavator with a 2-cu.yd. bucket. Dredge no. 4, working gravel along 
the American River near Fair Oaks, also used a dragline excavator with 
a 2-cu.yd. bucket. Operations were continued in 1942. 

Hoosier Gulch Placers, 1015 25th Street, Sacramento, operated a 
dragline dredge on Katesville Gulch and on the Logtown property in the 
Cosumnes River district during 1941. The dragline excavator had a 
2-cu.yd. bucket. A second dragline dredge served by a 2^-cu.yd. bucket 
was operated on the Hutchison property from January 5 to October 
31, 1940. This company operated boat no. 1 on the Biggs Ranch and 
boat no. 2 on the Rossi property throughout 1941 and during part of 1942. 

Humplireys Gold Corporation, 910 First National Bank Building, 
Denver, Colorado, operated a dragline dredge in the Cosumnes River 
district on the Fassett-Parker-Hanlon property from January 1 to Decem- 
ber 5, 1940. The equipment, which included a dragline excavator with a 
2i-cu.yd. bucket, was then moved to the Hutchison property where 
operations were continued during all of 1941 and from January 1 to 
April 6, 1942. In 1942 the floating washing plant was served by four 
dragline excavators, each equipped wdth a 2i-cu.yd. bucket. These were 
used to strip overburden as well as to deliver auriferous gravel to the 
plant. 

Lancha Tlann Gold Dredging Company, La Lomita Rancho, Locke- 
ford, operated a connected-bucket dredge at Sailors Bar, American River, 
from April 20, 1940 until November 11, 1942. The dredge is equipped 
with 84 buckets of 6-cu.ft. capacity and is electrically driven. 

Lohicassa Company, Box 812, Sacramento, operated a dragline 
dredge, with a 1^-cu.yd. bucket on the Mahon property from June 5 to 
October 17, 1940, when the property was worked out. 

McQueen and Downing, 1040 38th Street, Sacramento, operated a 
dragline dredg^ on Deer Creek in the Folsom district from September 
10 until December 17, 1940 and from January 1 to February 14, 1941. 

Natomas Company. See page 278. 



2fi2 PLACKK MINIXC I'OH f;()[,I) IN (AI.II'OHMA [ 1)11 1 1 . 1 :{.") 

Pdcijic Const Aijiivi (jnlis. Inc., 1401 4'Jiul Street, Saei-jiiueiito. 
reeovered 111 ounces of ^old and 11 oinu-es of silver as a b^-prodiict 
in the operation of a commercial sand and ^n-avel iilant at Fair Oaks in 
1042. In lf>4."{ this com]>any, tojrether with Fair Oaks (Jravel Company, 
reeovered 240 onnces of ^rojd and 21 ounces of silver. 

SAN BERNARDINO COUNTY 

The minei-al resonrccs of San I'.crnardino Coimfy liaxc been 
described by Tnckei- and Saiupsoii ' in the California .loui'iial of Mines 
and (leoiojry for October 104:}. Althoiijih this connly contains a wide 
variety of mineral de])osits of commercial importance, and althonjrh the 
repoi-t cited contains descriptions of many lode-jzold mines, little i)lacer 
miniiifr for ^old lias been done in the connt\' recently. 

If()( fli)if/ Bros., ]>ox 768, Sacramento, recovered i)lacer ^old as a 
b\-|)rodiict of an opei-ation carried on throiijihont 104.'{ principally for 
scheelite at the Sjmd Patcli mine in the Randsbnrjr district, (iravel 
amoniitiii".!- to "jUT.liif) cnbic yards was mined Avith a drajiline excavator, 
of which 1:U,9;U cubic yards wiM'e trucked to a stationary washing: ]ilant. 
The l)y-product production of iii-ecioiis metals was 210 ounces of <i<)ld 
and 45 ounces of silver. 

Ilolconih Vallcif Phiccr Conipduy, 91-i Xortli ^Nfain Street, Los 
An<ieles, opei-ated a non-flf)atin<i' wa.shinjr i)lant in the llolcond) Valley 
disti-ict, to which pi-avel was delivered by tractor and scraper from July 
7 to Xoveml)er 1(), 1041. Tlie yield from lfi,2(jr) eubic yards of {jravel was 
204 ounces oC jiold and 10 ounces of silver. 

SAN JOAQUIN COUNTY 

('(ilifi>nii/i (I'old Drcdf/iiKj Conipaiin, '.i'A California Street. San 
Francisco, operated an electj-ic connected-bucket drodjie witli 81 buckets 
of ()-cii.ft. capacity dnrin<>: 1040 and 1041. in the Jenny Tiind di.strict. 

(iold If ill Drxhjituj Coinjxnnf, :}11 California Street, San Francisco, 
operated two electric connected-bucket dred<ies on tlie Jenny Lucas, Alex 
IN'iie. Putnam. Tliorne, and Osterman properties in the Camanehe dis- 
li-ict dnrintr 1041. Some work was done in San Joafpiin County duriiifr 
li»40 also. One dred«je had (56 buckets of I'j cu.ft. capacity and the other 
had 87 buckets of 8J-eu.ft. capacity. Operations wei-e continued in 1042 
on some of the properties mentioned above and also on property of Cali- 
foi-nia liands, inc. and Central ]>ank of Calaveras duriiifr most of 1042. 
The company also ojierated one dred;:e at a time during' i)arts of 104:}. 

(iohl V(ill< If Dredging ConijKiny operated a diy-land washing plant 
to which jrravel was delivered by jrasoline dra<:line excavator with a 
•J-cn.yd. bucket at tlu' IMurdock Kanch in the Camandu' district from 
February 2.') to May 24, 1042. The yield fnmi 0,:n6 cubic yards of «;ravel 
was 8:{ ounces of }rold and 6 ounces of silver. 

Lohicdssa Companif, Box 812, Sacramento, operated a dra<:line 
dred^re usin*; a IJ-cu.yd. l)ucket on the Foster Ranch in the Camanehe 
district from January 1 to ^Fay 14, 1042. The property was then aban- 
(h)ned as worked out. 

MohdniniK Sdiid (iiid drard f'oiii pditg, 7)21 East Lodi Avenue, Lodi, 
l)rodnced a small (piantity of <rold as a bv-]>roduct in pi-eparing sand and 
•Travel for concrete a«r{rrep:ate durinjr 104.'i. 

' TucUtT, W. n., and Sampson, It. J., Mineral re."<ources of .San J'lrnardino County: 
Califurnia .lour. Mines and Geology, vol. 3;t, pp. 427-549, 1943. 



Sec. IV] MINES BY COUNTIES 283 

San Griico Compayxy and C. E.Grnwell of Angels Camp operated 
drajirline dredges on the IMcGurk property in the Bellota (Linden) dis- 
trict in 1940. Each operator used a dragline excavator with a l|-cu.yd. 
bucket. 

Smith-N otterman Company, 245 West Rose Street, San Francisco, 
operated a dragline dredge with a l|-cu.yd. bucket on the Elmer Cady 
and Lewallen Ranches in the Jenny Lind (Bellota, Linden) district 
during 194L The operation was continued in 1942 from January to 
March 26, and the yield from 93,105 cubic yards of gravel was 344 
ounces of gold and 14 ounces of silver. 

A. G. WatJxins & Sons of Linden operated a dragline dredge 
equipped with a 2-cu.yd. bucket during 1940 and parts of 1941 on the 
Calaveras River. 

SHASTA COUNTY 

A report on the mineral resources of Sha.sta County was published 
in the California Journal of Mines and Geology for April 1939,^ and a 
map of the county .shoAving locations of mines was included; also a table 
of mines giving references to older reports. All of the placer operations 
mentioned below were started after that report was written. A few 
earlier operations of similar nature are described in the April 1939 
Journal. 

B. H. K. Mines, Box 325, Orland, operated a dragline dredge 
equipped with a l^-cu.yd. bucket on the R. C. Connelly and Robert Litsch 
properties on Clear Creek from November 15 to December 31, 1941. The 
yield from 54.400 cubic yards of gravel Avas 339 ounces of gold and 48 
ounces of silver. The operation was continued from January 1 to May 
15, 1942, and the yield from 120,000 cubic yards of gravel was 760 
ounces of gold and 104 ounces of silver. 

/. P. Brennan, 1343 Butte Street, Redding, operated a dragline 
dredge on Tadpole Creek from January 1 until October 7, 1940, then 
moved the equipment to Champion Gulch and continued the operation 
until Jitne 1941. Both of these operations were in the Igo district. 
The dragline excavator was equipped with a l.j-cu.yd. bucket. 

Clear Creek Dredging Company, Box 598, Redding, operated a drag- 
line dredge using a IJ-cu.yd. bucket on Clear Creek in 1940. In 1941 
a second dredge wdth a 2|-cu.yd. bucket was added. This company 
operated in 1942 also. 

Columhia Construction Company, 1522 Latham Square Building, 
Oakland, prepared 1,781,466 tons of gravel to be used in the construction 
of Shasta Dam from a point upon the Sacramento River near Redding 
in 1940 and recovered a substantial quantity of gold. In 1941 this com- 
pany prepared 4,038,167 tons of gravel and recovered 2810 ounces of 
gold and 301 ounces of silver as a by-product. Two dragline excavators 
were used, one with a 5-cu.yd. bucket and the other with an 8-cu.yd. 
bucket. In 1943 the company produced 1,500,000 cubic yards of sand 
and gravel and recovered 1555 ounces of gold and 166 ounces of silver 
as a by-product. 

Crow Creek Dredging Company, Box 558, Redding, operated a 
dragline dredge on Crow Creek in the Igo district intermittently during 

lAverill, C. V., Mineral resourcts of Sha.sta County: California Jour. Mines and 
Geology, vol. 35, pp. 108-191, 1939. 

See also Averill, C. V., Gold dredging in Shasta, Siskiyou, and Trinity Counties : 
California Jour. Mines and Geology, vol. 34, pp. 96-125, 1938. 



284 



I'LACLR MINlNf; KOR OOIJ) IN CALIFORNIA 



I Hull. l.'M 



1940. Durinp: lf)41. 22().()0() cubic- yards of <i:ravpl wore delivered by a 
drap:line excavator with a IJ-cu.yd. bucket and were washed. In lf)42 
operations continued on Cottonwood Creek from January 1 to April 13, 
and 100.000 cubic yards of grave! yielded 580 ounces of j;old and 20 
ounce.s of silver. 

DcKarr and Herbert of Reddinjr operated a drajjiine dredj^e, usinf? 
a 3-cu.yd. bucket, on the Fred Kohle f)roperty on North Cow Creek from 
January 16 to March 17, lf141. The yield from 2:},8()0 cubic yards of 
gravel was 207 ounces of pold and 46 ounces of silver. 

Dobbin Gulch I)redgin<j Conijxmy, Hox ^)'-V.), l^edding, operated a 
dragline dredge with a 1 |-cu.yd. bucket, on the Montgomery property 
on 4<'lat Creek from January I'to May 80. 1!)41 . The yield from 142,160 
cubic yards of gravel was S'^S ounces of gold and ()2 ounces of silver. 
In 1942 operations were conducted on the Roaring River from March 3 
to June 2. The yield from 70,r)0() cubic yards of gravel was 169 ounces 
of gold and 11 ounces of silver. 

Fnnch Gulch Dredging Cunipani), 2404 Russ Building. San Fran- 
cisco, in.stalled a connected-bucket di-edge eriuipped with 76 buckets of 
4^-cu.ft. capacity on Clear Creek near French (Julch and began opera- 
tions on September 2. 1940. The operation was continued during 1941. 

C. E. Gruwcll, Hotel Redding, Redding, operated a dragline dredge 
on the Fish, Forschler, Rais. and Russell Ranches in the Igo district 
duriiig 1941. 

Lincoln Gold Dredging Contpang of Lincolr. operated a dragline 
dredge having a 2^-cu.yd. bucket on the Jii-ady ])r()perty in the Igo dis- 
trict in 1942. The yield from 87,284 cubic 'yards of' gravel was 162 
ounces of gold and 26 ounces of silver. 

R. S. Olaon, 1178 Walnut Avenue, Redding, operated a dragline 
dredge from January 1 to March 10, 1940, on Chiiia (Julch and from 
June 18 to December 5 on Daly dulch. P>oth are in the Igo district. 
Operations on Daly Gulch were continued in 1941. 

Pioneer Dredging Conipong, Box 80.1, Redding, opeiated a dragline 
dredge ecjuipped with a 8-cu.vd. bucket, in Happv Valley from Jainiarv I 
to 'August 21, 1940. 



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Roc. rv 



MINKS BY COCXTIKS 



28f 



Snu (iruco (\jnijiiinif, Koddiiij^, moved its dra<!:liiu' dred{:?e equipped 
with a n-cu.yd. bucket to property of the Happy ValU?y Land and 
Water Company and op(>rat('d from Xovember 1 until the end of 1940; 
also during; IfUl. 

Tehama Drcdfjiny Company, l>ox 727, Anderson, oj)erated a drag- 
line dred^^e. wliieh had a v(*»-yd. bucket, at the Gold Acres mine near 
(ias IV)int from ^larcli 20 to June .30, 1941. The yield from 48,860 
cubic yards of gravel was 242 ounces of gold and 17 ounces of silver. 

Thurman Gold Dredging Company, 235 ]\Iontgomery Street, San 
Francisco, installed a connected-bucket dredge equipped with 72 buckets 
of 9-cu.ft. capacity on Clear Creek and began operations on December 1, 
1940. Operations continued during 1941 and until October 14, 1942. 
SIERRA COUNTY 

Depot Hill hydraulic mine owned by F. J. Joubert of Campton- 
ville lias been operated practically every season for many years. Stor- 
age for the tailing is available behind the Rullards Bar dam of the 
Pacific (Jas & Electric Company. The mine is o miles north of Campton- 
ville on the .state highway nnming to Downieville in .sec. 19, T. 19 N.. 
K. !) E., ]\I. D. ]\Iore than a page of additional details about this mine 
is contained in the California Journal of Mines and Geologv for Janu- 
ary 1942.1 

Indian Hill )nine was described by Gardner and Johnson ^ as 
follows : 

B. F. Dyer operated the old Indian Hill mine near Camptonville 
during 1931 and 1932. Tlie material washed up to the end of 1932 con- 
sisted maiidy of slides from the faces of the old w'orkings. The gravel 
deposit was 35 feet thick ; the grade of bedrock was 1 inch to the foot. 

' Averill, (". V., Mines and mineral re.'^oince.s of Sierra Countv : California Jour. 
Mines and Oeolopry, vol. .''.8, p. 29, 1942. 

-c.ardner. E. D.. and John.son, C. H., Placer mininp in the western United States, 
I'art II, HydrauiicUinfi. etc. : r..S. I'.ur. Mine.'^ Inf. fire. (;7S7, i)p. r>(^-^)^, 1934. 




■-^•^ ^-.-^-. 



Depot Hill hydraulic mine. Reprinted from California Journal of Mines 
and Geology, January ii'Ji, p. Zi. 



286 



rLA( KR MIMN(! FOR OOLO IX CALIFORNIA [Bull. 135 




KiG. S!i. I'oviTty Hill I'ropifties drcdj^f lunlcr construction. h'citrinlrd ftotti (Utli- 
loriiifi ./oiiriKil of Miiiir. luid (!iiiUi<i\i. Jdiiiiari/ lH'iJ, p. -Ui. 




Hi. ;tO. JU-nioMhn ov.rl.uidcM 
Amador County. J'hoiii bx 



iiivlcNii ')) y((b(t .Mdintliicl iir>u(/ Vo)ii])(iiiy. 




Fig. 91. Willlatn RichUr and Sons diapline dredge. Reprinted from California 
Journal of Mines and Geology, January 19k2, p. 38. 



See. IV] MINKS nv counties 287 

Water was brought to llie luiiit' tlir()U<ili a !>-inile ditch and 3000 feet of 
22-iiK'h and 1500 feet of la-incli iiipc The head was 130 feet. One 
No. 6 giant with a 4-, 4|l-, or (i-ineli nozzle was used. Boulder.s up to 
14 inches in diameter were run tln-oujili tlie sluice boxes. The sluiceway 
was down a narrow gulch and consisted of .six sections of boxes (2 to 6 
boxes to the section) and the rock bottom of the gulch between sections. 
There was a drop of 10 or 15 feet at the end of each section of boxes. 
The fall and cascading down the rocky gulch between each section broke 
up all cemented material and washed the gravel free of clay. 

The boxes were 40 inches wide and 40 inches high ; the grade was 
i-inch to the foot. The upper five sections of boxes were paved ^yith 
wooden blocks; the riffles in. the lower section Avere of rock paving. 
Seventy percent of the gold was caught in the upper two boxes. Three 
undercurrents were used near the lower end of the line. The discharge 
of one luidercurrent went into the main sluice before the next was 
taken out. The grizzly opening for an undercurrent in the bottom 
of the main sluice was 18 by 40 inches. The grizzlies were of 1^- by 
3-inch iron bars set on edge 2^ inches center to center. Additional top 
water Avas run over the undercurrents from an opening in the side of 
the sluice. The. first undercurrent was 8 feet Avide by 24 feet long. 
The riffles consisted of rows of pine blocks 6 inches thick by 6J inches 
deep separated by H-inch crossboards. The second undercurrent was 
8 feet Avide and 20 feet long. The riffles consisted of 31- by 3i-inch 
angle iron -J inches thick and set crossAvise on 5-inch centers. The third 
undercurrent at the end of the loAvest box Avas 10 by 12 feet. The riffles 
Avere four angle irons 1 inch apart at the head of the undercurrent and 
rock paving from there doAvn. A crew consisted of seven or eight men. 
About 100,000 cubic yards Avas Avashed during the 1932 season at a 
cost of 8 cents per cubic yard exclusive of con.struction Avork. 

Loftus Blue Lead Mining Company, 801 Columbia Street, South 
Pasadena, operated a hydraulic mine in 1940 and 1941 on a large group 
of claims running from St. Louis to HoAvland Flat, a distance of 4 miles 
bv road, in sees. 31, 32. T. 22 N., R. 10 E., M. D. ; sees. 5, 6, 7, T. 21 N., 
11. 10 E. ; and sec. 12, T. 21 N., R. 9 E. In 1940 the yield from 60,000 
cubic yards of gravel Avas 352 ounces of gold and 25 ounces of sih'er. 
A few additional details about this mine are contained in the California 
Journal of ]\Iines and Geology for January 1942.^ 

Pioneer Project mine in sees. 13, 14. 23, 24, T. 21 X., R. 9 E., M. D., 
is a consolidati(m of the old Pioneer Avith the adjoining Comet, Chal- 
lenge, and Riffle claims. It Avas Avorked in 1942 and 1943 by A. J. Just, 
AV. II. Pike, and A. J. ]\Iodglin of LaPorte. Hydraulic operations for 
a period of 10 days in 1942 yielded 71 ounces of gold and 4 ounces of 
silver from 17,000 cubic yards of gravel. A sub.stantial quantity of 
gold Avas recovered during a 3-month period of operation in 1943. 

Poverty Hill Properties, 974 INIills Building, San Francisco, is a 
l^artnership of Avhich the general partners are A. J. Oyster, W. C. Van 
Fleet, Walter W. Johnson. Operations Avere conducted in 1940-41 on 
a part of the main La Porte channel, one of the old Eocene auriferous 
channels. The property consisted of 1100 acres in sec. 32, T. 21 N., 
R. 9 E., :M. D.. and sec. 5. T. 20 X., R. 9 E. The property Avas first 
Avorked bv hA'draulicking, but later a connected-bucket dredge Avith 



3 Averill, C. \.. op. cit., p. 2S 



2«8 



PI.AfF.R MINIXC I OK (loi.l) 1\ (ArJFOUNIA [Bull. 135 





Fio. 93. Ruby mine, underground slusher hoist. Photo by courtesy of L. L. Ifiiela- 
donk; reprinted from California Journal of Minea and Geology, January 19 i2, p. ->«. 



Sec. IV] 



MINES UY COUNTIES 



280 



82 buckets of fi-cu.t't. (•ai)acity whs instfilled in a pond in one of tlie 
hydraulic juts. Overburden was stripjjcd to a dei)th of 40 feet with 
cater])illar tractors and i-arryalls. A few additional details about tliis 
operation are contained in the California .Journal of Mines and CJeolofiy 
for January 1942.'* 

William Richtcr d Sons, Route 2, Box 400, Oroville, operated a 
dra<;line dred<>e ecpiipped with a l]-cu.yd. bucket on propei-ty owned 
bv the Pacific (las & Electric Comj^auy on the Yuba River in sees. Ki, 17, 
T. 19 N., K. 9 E., M. D., in 1941 and 1942. Tn 1!)41 operations from 
June 1 to December '.U yielded 140.'5 oinices of ^old and 179 ounces of 
silver from 280,000 cubic yards of <rravel. Tn 1942 operations from 
Jajiuary 1 to April 80 yielded 248 ounces of jjold and 29 ounces of 
silver from 58,000 cubic yards of iiravel. 

Ruby mine has been operated durinjr recent years by C. ^J. Best, 
800 Davis Street, San Leandro. In 1948 operations were on a main- 
tenance basis only because of Limitation Order L-208 of the AVar l*ro- 
duction Board. The yield from 500 cubic yards of jiravel was 828 
ounces of <rold and 12 ounces of silver. Becan.se of the newl\- developed 
methods of drift mininp- used at this mine, a description of the opera- 
tions in 1941 is reprinted below from the California Joui'ual of Miiu^s 
and Geologry for January 1942:"' 



Averill, C. V., op. cit., pp. 3.5-37. 
Averill, C. v., op. cit., pp. 38-42. 







i^"* 







t-«'#i 






^ :^ 



Fig. 94. Ruby mine, timbering-. Slusher scraper at left. Photo hy conrtt si 
L. L. Huelsdonk; reprinted from Calijornia Jonrnul ot Mines (ind (leohiau. Jinin 
131,2, p. il. 



290 



PLACER MIXING FOR GOLD IN CALIFORNIA 



Bull. 335 




tea; 



32 












?5^ 



Sec. IV] MINES BY COUNTIES 291 

llw Ruby ininc was beiiiji- opcrati'tl in 11)41 by C \j. l>est, Catorpillai- 
Tractor Company. San Leanclro, with L. L. Iluelsdoiik, (Joodyears Bar, 
in charge. InchuUiig a lease on the ^lott property, there arc 1,100 acres, 
of which 800 are patented, in sees. 10, 11,14, 1.1, t. 1!) X., K. 10 E., M. D. 
The mine is reached by If) miles of road from Downieviile, mostly steep 
monntain road, dirt snrface. 

The l^ald j\Iountain E.xtension cliannel, one of the oldest Tertiary 
channels, branches from the Bald Monntain channel at a point nortli 
of Forest. Bald Monntain channel is the same as the i\nby and City- 
of-Six channels. The last two named are simply continnations of the 
Bald Monntain chaiuiel to the north. The Bald ^lonntain Extension 
channel was workeil in the Knby mine in the nineties from an adit level 
driven from the side of the monntain on which the town of Forest is 
located. Present work is on the opposite side of the monntain. An old 
adit level (portal elevation 4,707 feet) was ntilized for a distance of 
1,800 feet. Work beyond that l)oint is new. The adit is in the Tightner 
formation for 3,320 feet, then in serpentine for 520 feet, then in gabl)ro 
and schist for 610 feet, then pas.ses into a second belt of serpentine. A 
point in the adit is 1,850 feet sonth of the common corner of sees. 10, 
11, 14, 15, T. 19 X., K. 10 E. The contact of the second belt of serpen- 
tine and the gabbro-.schist is 200 feet east of the point in the adit jnst 
described. The adit then continues in a general southeasterly direction 
to a point where a raise was put up to the intervolcanic channel. Dis- 
tance from the portal to this raise is 5,850 feet and the raise is 109 feet 
high. From the top of the raise 400 feet of drifting was done in a south- 
erly direction on the channel and 4,000 feet in north and northeasterly 
directions on the channel. From this point the channel winds consider- 
ably, and 700 feet more of driving will be needed to connect with the 
Larry shaft, of which the collar elevation is 5,163 feet and the bottom 
elevation is 4,954 feet. Several thousand feet of additional exploratory 
work have been driven on the channel, and a connection for air, involv- 
ing 3,000 feet of work, has been made to the Golden Bear shaft. 

The intervolcanic channel that is being worked is 200 feet lower than 
the Bald ^Mountain Extension channel and cut off the Bald Mountain 
Extension channel. Apinirently much of the gold in the intervoleanic 
channel was derived from the older ehannel. The intervolcanic channel 
varies from (JO feet to 160 feet in width and is breasted to a height of 
6 to 8 feet. Channels are capped by as much as 900 feet of lava, which 
is mostly andesite, but basalt is found on top of the andesite in i)laces. 
Large bouldei-s are stored underground. Tlie finer gravel is moved by 
slusher scrapers to raise-chutes and hauled in trains by storage battery 
locomotives to the washing plant at the portal (tf the main ailit level. 
Timbering comprises .stulls and caps specially designed with a mortise 
and tenon and handled by one man. 

In the sunnner of 1941, the crew comprised 18 men, and 80 to 100 
tons of gravel were treated per day, but when the crew was 43 men, 
200 tons were treated per day and a maximum of 250 tons was reached. 
The reason for the small crew in 1941 was that many men had left to 
engage in defense activities Gravel passes from storage bin over Hun- 
garian riffles of alloy steel 50 inches wide by 1^ inches deep ; tlien to a 
vibrating screen, which is a double screen. The upper screen is of 2-inch 
square openings, and rods are half an inch in diameter. The screen which 
is below is four-mesli of Xo. 12 wire. T'ndersize goes to a six-unit Huels- 



202 l'LA( i:i« MINING FOR GOLD IX CALIFORNIA [Bllll. 135 

(loiik taldc 20 feet Ion;: l)y 7 feet wide. The washing plant will treat 
')()() tons of ^TJivcJ piT 24 lionrs. The screen mentioned above is vibrated 
by an eccentric and 2()-lii). motor with a .'^]-inch stroke at the rate of 200 
vibrations per minnte. Tndersize goes to the Iluelsdonk table mentioned 
above, which is vibrated with a ^-inch to 1-ineh stroke at a rate of 200 
vibi-ations per minute. The end of the table farthest from the vibrating 
screen is set three-(piarters of an inch lower than the end near the screen. 
Uecovcry amonnting to 10 to 2X) percent of the total is made on this table 
as fine gohl. The remainder is made on the first riffle and the screen 
abont (vjnaily dividctl. Steel bars are placed across the screen to hold 
it down and these have a tendency to act as riffles. Below the screen 
additional i-iffles ai-c provided in the sluice tliat carries away the oversize, 
but little gold is recovered from these. Nuggets as big as 52.33 ounces 
valued at $1,758 have been recovered. C. L. Best is saving all nuggets 
al)ove $100 in value for exhibit purposes and in 1941 had a collection of 
123 that had been recovered since 1937. Gold is 940 to 950 in fineness, 
^lost of the tailing is stacked on the property by means of a belt conveyor. 

The second .serpentine belt mentioned above is 490 feet wide, then 
the woi-kings pass into the Blue Canj'on slate, which is the bedrock of 
the channel being worked. On the contact of the second serpentine belt 
and the IJlue Canyon formation i,s a fault called the Independence, on 
which is a (i-foot (juartz vein. Another quartz vein 4 feet in widtli was 
cut 110 feet farther ahead in the adit in the Blue Canyon formation. 
A thii'd vein known as the Wolf vein strikes north and dips 65° W. 
It is (i inches to 12 feet in width. This vein was worked in the years 
1!>35, 193(), and 1937 to a depth of 200 feet below the main adit level. 
Drifts were run north on the 200-foot level for 600 feet and the ore 
was stoped through to the main adit level. This work on the quartz 
vein had been discontinued and the workings are now full of water. 
Ore was treated in a stamp mill of 30 tons daily capacity, and treatment 
was amalgamation on plates followed by tables and flotation. The quartz 
averaged $5.80 |H'r ton in the mill but additional gold was recovered as 
high-grade. This vein is in the Tightner fornuition and was found at a 
distance of 2,120 feet from the portal of the main adit. 

Cam)) facilities ai'c provided for a crew of 40 men, and the property 
is well e(|uii)i)e(l with r('i)air sh()j)s, drill sharpeners, air compressors, 
and other modern machinery. Electric power is supplied by Pacific Gas 
and Electric Comi)any. 

Tennessee Mausmon drift mine was worked throughout 1942 by 
C. S. I*oor. The yield fnmi 1,200 cubic yards of gravel was 142 ounces 
of gold and l(i ounces of silver. In 1943 ojierations from January 1 to 
Xovember 1 yielded 74 ounces of gold and 8 oiuices of silver from 680 
cnbic yai'ds of gravel. 



Sec. IV] MINES BY COUNTIES 203 

SISKIYOU COUNTY 

Beaver Dvechjing Company, 615 F Street, Marysville, ^vorked a 
dragline dredge with a 5-eu.yd. bucket on Indian Creek 6 miles west ol" 
Fort Jones from April !(> to December ;?!, 1!14]. 

C. & E. Drcdiiinn ronijHinif. 1002 Pacific Building, Portland, Ore- 
gon, operated a dragline dredge using a 2-cu.yd. bucket on Mc Adams 
and Cherry Creeks in the Deadwood district from May 9 to December 
31, 1941. 

Cal Oro Dredging Companjf, 681 Market Street, San Francisco, 
operated a connected-bucket dredge on the Lange property in the Green- 
horn district from January 28 to September 22, 1940. 

Etna Gold Dredging Companxi, 1730 Franklin Street, Oakland, 
operated a connected-bucket dredge with 80 buckets of 3-cu.ft. capacity 
on Wildcat Creek 2 miles north of Callahan in 1940. The yield from 
800,000 cubic j'-ards of gravel was 4299 ounces of gold and 642. ounces of 
silver. The operation was continued until October 1941. 

Farnsworth mine in the Liberty district was operated by the 
hydraulic method by E. A. McBroom from March 1 to May 10, 1943. 
The yield from 500 cubic yards of gravel was 22 ounces of gold and 2 
ounces of silver. See Salmon River Mining Company also. 

The Gallia Placer Mining Company^ operated the Gallia mine on 
the North Fork of the Salmon River near Sawyers Bar during the 1932 
season. The gravel was 30 to 35 feet thick and contained some large 
boulders. Water was brought to the mine under a 265-foot head through 
a 2000-foot line of 36- to 15-inch pipe. Enough grade was riot available 
for the disposal of tailings, and the gravel as mined contained too many 
boulders for the successful operation of a hydraulic elevator. The 
gravel was cut and swept to a Ruble elevator by a giant with a 3i- or 
4-inch nozzle. It was then put through the elevator by another giant 
with a 4^-inch nozzle. The Ruble was 4 feet wide and elevated the over- 
size 25 feet. The Grizzly consisted of 90-pound rails 2h inches apart set 
lengthwise on 10- by 10-inch stringers. The undersize from the grizzly 
went through a 24-inch sluice with riffles consisting of angle iron and 
rails placed crosswise in the boxes. 

The sluice discharged into a hydraulic elevator with a 20-inch intake. 
A 4-inch nozzle was used in the high-pressure jet ; the material' was 
elevated 30 feet. The elevator discharged into a second sluice. 

The capacity of the plant Avas limited by the quantity of material 
that could be run over the Ruble elevator. The cutting and driving 
giant was used for a few hours and then shut off until the accumulated 
material could be handled in the Ruble. The giant at the Ruble oper- 
ated continuously. About a week with the full crew Avas required to 
move the Ruble ; it had to be moved every 3 weeks, as the dump room 
behind it was exhausted. 

Boulders too large to go up the Ruble were moved back by a derrick. 
Large boulders uncovered in cutting were dragged from the pit by means 
of a donkey engine. Water was used not only for the giants in the pit 
and the jet of the hydraulic elevator but also for operating the derrick 
and running a dynamo for operating a sawmill and an air compressor. 

^ Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, 
Part II, Hydraulicking, etc. : U.S. Bur. Mines Inf. Circ. 67S7, 1934. 



2!)4 im-A(i:k ^iinint. i-ok cof.d in cAuroHNiA [Bull. 135 

The workiiiir ci-ow consisted of two men in tlio jiit and oiio man on 
tlio ditcli liiu^ on cadi of two 12-lioiir shifts. Alth(»u<rli •")() to (50 fnhi<' 
yards por hour could ho cut and swept to the IJuhle hy the cuttinp-^iant. 
the avera-rc capacity, includinjr the time for moving' the I\>il)h\ was 200 
euhic- yards per (hiy. The lal)or eost. assumin^r ^^ per man-shift, would 
he 11 cents per cubic yard. The eost of supplies would he about 2 cents 
and supervision 4 cents, makin<:- the opei-atin^i' cost 17 cents. 

I[nf>i)ii f'diiii) Drahfliifi Cain paini. Happy Camp, ojx'i-ated a dra^'- 
liue dredt«e on the Allen property from May 1 to .May :{1. 11)40. The 
dredfre was then moved to ])roi>erty owned i)y (Irani Smith and was 
ojierated there from September 1 to November .'^0. 

Horfon diilrh Mint was described by (Jardnor and -lohnson- as 
follows: 

J. (). ^FcUroom operated the llortou (luleh i)laeers on the Soutli 
Fork of the Salmon River near CVeilville. The 1032 sea.son extended 
from January 1 to April 11. The <rravel was fairly ti<rht. The jrrade 
of bedrock was 1 inch to tlie foot. One <iiant with a o-inch nozzle, work- 
iiiff under a G.l-foot head, was used for both cuttinjr and sweepin<r the 
jrravel into the .sluice l)oxes. About 30 inches additional by-wash water 
was u.sed for movinji' the '^i-avel throujrh the sluice which consisted of 
three 12-f()ot boxes 24 inches wide. The riffles were hard boulders liaiid- 
shajH'd to make a pavement 7 to 10 inches thick. A)i undercurrent was 
u.sed for 1 month and then discarded ; about 1 ounce of pold was cleaned 
up from the undercurrent durin«r the month's run. All larjre boulders 
were blasted. An averajje of 80 cubic yards per day was w^ashed durin«r 
the 1932 season. Two men were employed. At $3.50 per shift the 
labor eo.st would be f) cents; supplies would amomit to about 2 cents 
per cubic yard, makiiifr a total of 11 cents. 

Jonhert mine in the Liberty district was worked by lessees, H. J. 
Dickinson, Stanley Czerwinski, and others of Sawyers Bar in 1940 and 
1941. Hydraulic operations in 1940 yielded 354 ounces of f?old and 55 
ounces of silver. In 1941 the yield from 27,900 cubic yards of gravel 
was 385 ounces of jrold and 58 ounces of silver. 

Larsen Bros, and Ilarnis Bros., Route 4, Box 2220, Sacramento, 
operated dragline dredges on the Klamath River and on Horse Creek 
during 1940 and 1941. In 1943, 114 ounces of gold and 18 ounces of 
silver were recovered from concentrates accumulated at the Moccasin 
dredge before it was clased because of War Production Board Limitation 
Order L-208. The following description of operations in 1940 are 
reprinted from the California Journal of ]\Iines and (Jeology for April 
1941:3 

Scandia mine, in sees. 7, 8, 9, 15, T. 4(5 X., R. 10 W., M. I)., on Horse 
Creek near the Klamath River, was being operated in 1940 by Lar.sen 
Bros, aiid Harms Bros., Route 4, I>ox 2220, Sacramento. Emmet Miles, 
Hor.se Creek, Siskiyou ('ounty, was in charge at the mine. The property 
is reached by means of 2 miles of dirt road turning from the graveled 
state highway along the Klamath River. 

a Op. clt. 

■■• Averin, C. V., DragUne dredglnj? in Siskiyou County : California Jour. Mines and 
Geology, vol. 37, pp. 328-331, 1941. 



Sec. IV] 



MIXES HY COUXTIES 



29." 




reilge at Scandia mine. 



Low bar.s of Iloi'se Creek for a total length along the creek of 6 miles 
Avere being dredged. The width was abont 1,000 feet in the lower part 
of the tract but less al)ove. Depth of gravel was 12 feet to 18 feet and 
practically all the gold was in the lowest 2 feet. From a tract of 100 
acres about 2,000,000 cubic yards had already been dredged in the fall 
of 1940. 

The washing plant is of Bodinson make and is similar in all respects 
to the ones described in the chapter on dragline dredging (ante). 

It is of 3,600 bank-yards capacity per 24 hours and is built to serve 
a 3-cu.yd. dragline excavator. The bucket in use is a 2j-yard Esco. The 
trommel is punched with f-inch to f-inch holes, and nndersize goes to 
standard-dredge-type Hungarian riffles. Murphy 6-cylinder diesel 
engines rated at 160 hp. each supply the power on both the excavator 
and the washing plant. 

The following figures on cost of equipment and cost of operation 
were furnished by Emmet Miles: 95 Northwest dragline with 60-foot 
boom, $58,000 ; washing plant, $40,000 ; D7 tractor with bulldozer, $7,000 ; 
D8 tractor with carryall, $10,000; truck, welder, pickup, $1,900; miscel- 
laneous lighting plants and pumps, $1,000; air compressor, $200; spare 
generator for washing plant, $900. The last item mentioned furnishes 
power to an electric motor on the upper end of the belt stacker. The 
total crcAV comprises 14 men. 

Gravel actually washed on boat cost 5 to 6 cents per cubic j'ard to 
handle. Cost of removing and leveling overburden was 7 cents per cubic 
yard. No depreciation was included in these costs. To cover the cost 
of mining, stripping overburden and leveling, including depreciation 
but excluding profit, it was necessary for the gravel to run 10 cents per 
cubic yard. 

Restoration of the land in order to make it available for farming 
appears to be an accomplished fact at this mine. A tract of 100 acres 
is being so restored, ^nd 60 acres were to be planted to new crops, alfalfa, 
rye, and sweet clover in the fall of 1940. Some of the fields were already 
green with the new crops in October, 1940. 



2!)() 



PLACKR MINING FOR GOLD IN CALIFORNIA 



[HuU.l.'Jo 



The laiul alon": the creek averajres 1,000 feet in widtli. It carries 
an ovcrhiinleii of soil o to 6 feet in deptli. For dredfrinpr, it is divided 
into strips roujrhly MOO feet in width. P"'roni tlie first strip the soil over- 
burden is removed to wasteland aloiifr the outside of the tract. This i.s 
done with a D8 Caterpillar tractor and a carryall of 12 cubic yards 
capacity. At times a second outfit of 16 cid)ic yards capacity has been in 
use. After the soil has been removed from the MOO-foot strip, the jrravel 
beneath is dredged with tlie drajrline to a depth of 12 to.lH feet. The 
belt-stacker on the dred«ie leaves the gravel behind in conical piles about 
20 feet hij;h. Next a Caterjiillar tractoi- with bulldozci- attachment levels 
these inles, and the runninjr back and foi-th of the heavy machine packs 
tlie jiravel considerably. Then the soil of the second :iOO-foot strip is 
removed by the carryalls and placed on the leveled <rravel of tlie first 
strip, and is spread out and <iraded so tliat the land is ready for farminjr. 
The process is continued to the last strip, where the <ri'avel is spread in 
the form of a dike to hold tlie stream in a i)rei>ared channel. l*i-eviously 
the stream i-an near the center of the tract and {Jfave trouble from floodinjr 
and washin^^ the land. Hence, the operators believe that the land is left 
in better condition for farming- than it was orifrinally. 

Efforts have been made in the ])ast to level the pravcl fi-om a drcd;.'e 
and to throw out the fines directly from the dredge on top of the f?ravel. 
Disturbinjr of the {iravel by the dredjre results in an increase of voids 
between the various boulders and cobbles, and the fines jro into these 
voids to a jireat extent. Even if soil is left on top. it may jii-adnally sink 
to fill the voids, leaviufr iiravel and boulders exposed on the surface. The 
present method overcomes the difficulty in two ways : the lieavy machines 
pack the jrravel. and the five to six feet of soil put on top <rives a wide 
mar«rin of safety. 

Unfortunatt'jx- this method can not be api)lied to all drcdjrinjr-land. 
First, the avei-aj:e tract does not contain such a thick layer of jiood soil. 
Second, the method is expensive, and the averajze tract does not contain 
enoujih jrold to jiav for it. The operators fi<rure that the extra cost of 
restorin«r the land was .H<2(),0()0 for a tract that is worth less than $10,000 
as a farm. As an example of the expense in\dlve(l, consider the fact that 
one ti-actor woi-tli about $H,0()() had alreadv been worn out in rou":ld\- 




Fii;. 'j7. Dragline ilr.ilm- at Mi^cca.sin min<-. 



Sec. IV] WINKS BY COUNTIES 297 

a year and a half, and in the fall of 1940 a second was well on the way 
to being worn out. 

However, the land along Horse Creek contained enough gold to 
pay for the restoration and a profit besides. The original restored tract 
was used to induce the owner of an adjoining tract to allow his land to 
be worked by the same method, so the Avhole operation is profitable. 

Moccasin mine, in sec. 14, T. 4(i X., K. 10 W., M.D., was also operated 
by Larsen Bros, and Harms Bros., Route 4, Box 2220, Sacramento, in 
1*940. The property is on the Klamath Hiver about li miles up the river 
from Horse Creek. It is reached from the bridge at Horse Creek by 
means of a road up the nortii bank of the river. A river bar about 2,000 
feet wide cari-ying gravel to a depth of 18 feet to 35 feet was being 
dredged. Total depth in some places including 10 feet of fine over- 
burden was 45 feet. 

The Moccasin outfit includes the largest dragline excavator used for 
dredging in northern California. The only larger dragline used for any 
purpo.se is the one that excavates gravel from the Sacramento River at 
Redding for aggregate to build Shasta Dam. The 5-yard :\lonighan at 
Moccasin mine walks around much as a man walks and is equipped with 
a large foot on each side for that purpose instead of the Caterpillar treads 
commonly used on smaller draglines. It has a 100-foot boom and is 
capable of digging to a depth of,45 feet. The bucket in use is a 4i-cu.yd. 
heavy-duty Esco. 

The washing plant is of Bodinson make and has a capacity of 6,000 
cubic yards per 24 hours. Tlie trommel is 47 feet by 72 inches and the 
largest holes are three-quarters of an inch. All (abrasion resistant) steel 
used on the first section of the trommel had given 7i months of service 
in the fall of ]!I4(). The pumi) is a 14-iiu-h United Iron Works pump 
driven by lOO-lip. (Jeiieral Electric motor. The 85-foot stacker carries 
a 42-inch belt. The barge is 40 feet Avide by 64 feet long by 54 inches 
deep. Power is furnished by a :{00-hp. Fairbanks ]\Iorse diesel engine on 
each machine, the dragline and the washing plant. The engine on the 
washing plant di-ives a 200-kva. Fairbanks Morse alternator, 480 volts. 
]?oil-boxes similar to those used by Lincoln Gold Dredging Company in 
Ti'inity County are used under the trommel. A manifold supplies jets 
with Avater under pressure in the various compartments beneath the 
trommel and thus the sands are kept in agitation. 

The overburden, 10 feet in depth, is removed aiul piled to one side 
by means of a D8 Caterpillar tractor and a 12-cu.y(l. carryall. No attempt 
is made at resoiling as at the Moccasin mine. The river was to be 
turned into a channel prepared for it on the north side of the tract 
during the winter, 1940-41, so that the present channel of the Klamath 
River could be mined. Near the river the gravel is. free of overburden 
and is 18 feet in depth. The width of the pond being carried in 1940 
was 500 feet. 

Costs of principal items of equipment set up on the job were 
furnished bv R. II. Wallace, superintendent, as follows: Monighan, 
$75,000 ; washing plant, $70,000 ; D8 tractor and carryall, $16,000. The 
total cost of operating the equipment per cubic yard of gravel was 
stated to be 9 cents. 

Lincoln Gold Dredging Company, Lincoln, operated a dragline 
dredge equippedAvith excavator having a Ij-cu.yd. bucket on the Calkins 



208 i'LA( i:k mimxc I(»i< (Kir.D i\ cAr.iioHMA | l)iill. Ill') 

property 1 mile rjist of VrcUa from .July 7 to Dci-cnibcr 2, 1!>41. Tlio 
yield fi'oin !K},742 ciiltie yards of jrravel was .").")(; ounees of jrold and 78 
oiniees of silver. In addition. E. A. KinUle recovered a small (piaiitity 
of jrold hy nsin^ a dry-land plant. The same two operators also worked 
the Hose projierty. In 1!>42 the company operated a drajriine dred«.!e on 
several properties as follows: from j)ropei'ty owned by the City of Vreka 
the yield was .'{()4 ounces of <r(»ld and 44 ounces of silver from 4:{.()2!) 
cubic yards of jii'avel ; fi-oiri (Jeneral Dredjjre property the yield was 1844 
(Unices of ^'■old and 2iV.i ounces of silver fi-om 272,42."i cubic yards of 
pravel ; and from the \unes projiei'ty the yield was 2.')I> ounces of <rold 
and .'{7 ounces of silver fi-om .■M.12H cubic yai-ds of gravel. All of these 
pi-operties are in the (Ji-eenhorn district. 

MtQii(cn and Downiiic,, 12") Dexter Sti-eet, Vi'cka, ojx'ratcd a di-a«r- 
line dred^a' on the Xeville and Silva ])i-o|KM-lies in the Klamath River 
district durin-r U»41. 

Midhind Comjxtiui, Inc., 1112 Pearl Street. Alameda, operated a 
drafrline dredjic which had a li-cu. yd. l)ucket on the Xorth Fork of the 
Salmon Hiver in Libei-ty disti-iet throu^liout lf)41. The yield from 
:{.")(), ()()() cubic yards of <rravel was l!l.")() ounces of <rold and 284 ounces f)f 
silver. 

Norfhcrn Drrdgiinj Coinj)anij, '^^]0 Kearny Street, San Francisco, 
ojierated a drajiline dredp:e on tlie Allen ftnd the Collins properties in tiie 
Klamath River di.strict from January to ^h\y 1041, when the company 
was dissolved. A drajriine excavator with a 2-cn.y(l. bucket wa.s used. 

Okoro Mi)ic.<t, Inc. of Callalian operated a drajrline dredjje inter- 
mittently from January to June 1040 and washed 4;3,()0() cubic yards of 
p:ravel, from Avliich 218 ounces of <ioId and 31 ounces of silver were 
recovereil. In 1041 operations coiulucted from July 11 to December 31 
with a di-a;:line dredjrc efpiipped with a. 22-cu.yd. bucket yielded 771 
ounces of <rol(l and 101 ounces of silver from 24r),000 cubic yards of 
fri-avel. In 1042 ojierations with tlie drajrline di-ed^e on the Ilayden 
property during: the month of January yielded 103 ounces of j^'old and 
10 ounces of silver from 60,000 cubic >ards of irravel. 

())•() TriuH\i Drcdgiiu/ Coinixnuf, liox 212, Oroville, ojierated a draj?- 
line dredjre which had a 1 '-cu.vd. bucket on Scott River during 1040 and 
until May 31, 1041. 

/*. I). Sdcchi, K. L. Sjxlh )il>(r(i, and F. Kiddi, of Areata, operated 
a drajrline dredjre usin^r a H-cu.yd. bucket at forks of Salmon inter- 
mittently durin*.'- 1040. They recovered 'Mi7) ounces of gold and 53 ounces 
of silver, 

Salmon Ifii'cr Gold 1)nd<i'n\<i ('ninjxiin/, 310 Kearny Street, San 
Francisco, operated" a drajiline dredfre. usiujx a 3-cu.yd. bucket on several 
properties in the Salmon River district durinp: 1041. 

Salmon River Mining Companxf property was described by (lardner 
and .Johnson^ as follows: The Farnsworth brothers operated the mine 
of the Salmon River Minin«r Com])any on the South Fork of the Salmon 
River near Cecil villc dui-in<r tlie 1032 season. The "travel consisted of 
G feet of pay dirt overlain with 11 feet of overburden. The grade of the 
bedrock was three-fourths of an inch to tlie foot. Water under a 22;)- 

♦Op. cit. 



Sec. IV'] MINKS 15V rorxTiics 299 

foot head was l)r()ii<zlit lo the mine tlii-ouji:li a :.}-inile ditcli and 1 mile of 
pipe line. The diameter of the fii-st :50()() feet of the pipe line was 22 
inches. This was reduced to IS and then to 1") inches at the pit. The 
branch line on the floor of the ])it to the different ^riants was of 11-inch 
pipe. Foui- jiiants with (J-inch noz/les weie set H|) in the pit, but only 
two were used at a time. A fifth <riant with a ")-incli nozzle was set up 
at the lower end of the sluice. I'sually one <;iant cut the bank and one 
of the same size swept the {Travel to tlie head of the sluice. The river ran 
alonjiside of the {jravel bein«>' washed, and the sluice box emptied into it. 
The river water carried the sand and fine jiravel downstream; coarse 
nuiterial, however, piled up in the stream. The dump giant was used 
1-2 to 2 lioui-s dui-ing the working shift to stack the coarse material at the 
end of the box. At the end of the washing shift this giant was set with 
an automatic control so that water played on the boulders until the next 
moi-ning. A windrow of boulders 80 feet high along the opposite bank 
of the rivei- had been made by the giant. The largest boulders were 
washed to tlie top of the pile. The stream played in a vertical arc; it 
was depressed slowly and went up faster. About 1 minute was con- 
sumed in each cycle. The giant was overbalanced so that the stream was 
elevated Avhen free. It was pulled downward by means of a 2-inch 
hydraulic cylinder fed through a hose from the pipe line. At the end 
of the stroke a trip turned a valve which shut off the water to the 
cylinder; at the top of the upward swing anothei- trip opened the water 
valve. Each morning the river bed at the end of the sluice was free of 
boulders. 

The sluice boxes were 36 inches wide by 30 inches liigh and were set 
on a grade of 7 inches to each 12-foot box. One setting of the sluice-way 
was sufficient for a season's work. The head boxes were protected by 
parallel roAvs of 6-inch poles placed horizontally on either side of the 
box. The i)oles were laid on an earth fill, the surface of Avhich slanted 
upward at an angle of 25° from the edge of the boxes. At the end of 
the season the poles Avere removed and the underlying gravel Avas Avashed 
into the boxes. The riffles in the sluice consisted of rock paving. 
Diorite boulders with one flat side Avere selectee from the Avashed gravel 
in the pit. These stones Avere dressed by hand to make a rigid paA-ing 
Avitli a fairly smooth npper surface. Formerly Avooden blocks were 
used, but they had to be replaced every 60 to 70 days. The sluice was 
cleaned up at the end of the Avashing season. An undercurrent was 
used at the loAver end of the sluiccAvay. The screen consisted of f-inch 
round steel rods 15 inches long, placed ^ inch apart lengthAvise Avith 
the sluice. The undercurrent table AA-as 5 feet Avide and 11 feet long; 
wooden Hungarian riffles Avere used. Quicksilver Avas used in the sluice 
box ; some reached the undercurrent Avhere it Avas caught in the riffles. 

Boulders up to 18 inches in diameter Avere put through the sluice. 
A hand derrick Avith a 25-foot mast and tAvo 30-foot booms Avas .set at the 
head of the sluice to remoA'e any oversize boulders that Avere Avashed to 
this point. A derrick hoist AA-as used for dragging stumps and large 
boulders from the main part of the pit. The hoist pulled over a 25-foot 
mast guyed Avith 4 lines ; apparently, hoAvever, 5 lines should have been 
used. The cable (11 inches in diameter) was pulled out by hand; the 
range Avas 400 feet from the hoist set-up. The hoist Avas double-geared 
and was run by an undershot Avater Avheel driven by a 1 J-inch nozzle. 
A stream from a 1-inch nozzle Avas used on top of the water Avheel for 



300 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 133 

braking!:. No exjilosivcs were used in the mine. The overburden was 
washed from the top of the fjravel and i-un directly into the river. This 
work was done dnrin<r lo\v-\vatei- periods when enough water for only 
one giant was available. 

Lumber cost $30 i)er M. An averajre of 223 cubic yards was worked 
per day during the 11)32 season. The opcratinjr cost was 7 cents per 
cubic yard with lal)or at H cents. 

Shasta Drcdgitu/ Coiiijxniy (Thompson dredjre), 737 North Central 
Avenue, Stockton, operated a dra^dine dred<re on Hrasswire Gulch 

1 mile southwest of Iloridirook from May 12 to August l(i, lf)41, after 
movinj: the equijiment from the .lemiy liind district in Calaveras County. 
The dragline excavator was equipped with a 2J-cu.yd. bucket. 

Surveyor's Mistake mine on Vesa Creek in the Klamath Kiver dis- 
trict was operated by Henry Beauman of Klamath River Post Office, 
during 1941. He used a non-floating washing plant to which gravel 
was delivered by mechanical means. 

Von der Hellen and Webber, Box 217, Yreka, operated a dragline 
dredge using a 2-cu.yd. bucket on Humbug Creek throughout 1940. 
The operation was continued from January 1 to October 1, 1941. 

yVilliam von der Hellen Mining Company, Box 1026, Medford, 
Oregon, operated a dragline dredge with excavator equipped with a 
2^-cu.yd. bucket on the Klamath River throughout 1940. In 1941 the 
operation was continued, and tlie yield from 773,700 cubic yards of 
gravel was 6113 ounces of gold and 928 ounces of silver. The operation 
was continued at McConnell Bar from January 1 to September 27, 1942, 
with a 3-cu.yd. bucket and the yield from 596,800 cubic yards of gravel 
was 3594 ounces of gold and 554 ounces of silver. 

Yreka Gold Dredging Company, 351 California Street, San Fran- 
cisco, completed its operation 2 miles north of Yreka in 1940 and then 
moved its dredge to Seiad Valley, where operations were resumed on 
September 14. 1940. The dredge was equipped with 67 buckets of 
6-cu.ft. capacity. The following description is repainted from the Cali- 
fornia Journal of Mines and Geology'' for April 1938: 

Yreka (iold Dredging Company built a new dredge in 1937 to 
work in sec. 14, T. 45 N., R. 7 AV., M. D., and adjoining sections along 

2 miles of Yreka Creek just north of Yreka. Ethredge Walker is presi- 
dent and Albert Schubach is secretary, Balfour Building, San Fran- 
cisco. Eric Peterson is dredge-master at Yreka. The dredge was built 
by \yalter AV. Johnson Company. Balfour Building, San Francisco, and 
the following details are furnished through the courtesy of that company. 

The hull is approximately 82 by 42 by 7 feet, and is made of 19 
pontoons about 20 by 10 by 7 feet, weighing 6 tons to 7 tons each. 
Exposed walls are made of V'^j-inch steel and inside walls adjacent to 
othei- pontoons are of ,-',;-inch steel. The pontoons and all structural 
parts, the digging and stacking ladders, frame for revolving .screen, 
distributors, and 10-ton spud are of electric- welded construction, which 
has proved very satisfactory. 

The bucket-line carries buckets of 6-cu.ft. capacity each, to dig to 
a depth of 25 feet. Buckets are of the new rivetless-lip, bowl-shaped 

^Avcrill. C. v., Cold dredging in Shasta. Siskiyou, and Trinity Counties: Califor- 
nia Jour. Mines and (Jeology, vol. 34, pp. 123-125, 1938. 



Sec. IV] MINES BY COUNTIES 301 

clesign, and are made of mani!:anese steel by American Manganese Steel 
Company, Oakland. Lower tumbler is made of manganese steel and 
is round ; upper tumbler is of high-carbon steel, six-sided, and cast 
integral with shaft. The hopper-chute is lined with manganese steel 
bars. A. special feature of this is a removable back plate for dis- 
charging boulders too large for the revolving screen. The boulders are 
dumped, without stopping the bucket-line, on a fork made of heavy 
bars. These are swung by a heavy shaft operated by a compressed-air 
cylinder to dump the boulder into a steel-lined chute which discharges 
into the pond. Dumping is regulated by a gate in the chute, so that 
the boulder can be placed in some part of the pond where it will be 
out of the way. 

The revolving screen is 34 feet long by 6 feet in diameter, and is 
lined with manganese steel plates. Perforations are f-inch to ^-inch 
and f-inch to f-ineh in the sections of screen except the last, which has 
f- by ^-inch slots for recovery of nuggets. Several feet at each end of 
the screen are not perforated. Undersize from the screen is treated 
on 1600 square feet of riffle-tables. Riffles are of angle-iron, l-j% inches 
by Ijjr inches spaced at 1 inch ; also of wood, some shod with steel, some 
with rubber. They are IfV inches deep spaced at 1 inch. Oversize from 
the screen is stacked by a stacker 90 feet long carrying a 36-inch Amer- 
ican Rubber Company rib-stacker belt. 

Water is pumped from the pond by Byron Jackson pumps of 
82 percent efficiency. The 10-inch high-pressure pump furnishes 3200 
gallons per minute at 65 feet head to the revolving screen. The 8-inch 
low-pressure pump furnishes 1800 gpm. to the riffle-tables. A 4-inch 
pump is provided for cleanups, washing decks, and fire-protection. 

The wdnch is a combination ladder-hoist, swing-line and spud-line 
winch controlled entirely by compressed air. This method of control 
adds to the efficiency of the dredge. A two-speed, specially designed 
motor delivers 55 hp. at 1200 rpm. or 35 hp. at 600 rpm. At the higher 
speed, it provides ample power for rai.sing the digging-ladder, raising 
the spud, and swinging the dredge when stepping ahead. The low 
speed is used for swinging during regular digging. 

Other electric motors are as follows : 100-hp. variable-speed on the 
bucket-line, 60-hp. on the high-pressure pump, 15-hp. on the low-pressure 
pump, 40-hp. with reduction gearing on the revolving screen, 25-hp. 
with reduction gearing on the stacker, and 3-hp. on the fire-pump. 
Power is transmitted by the bucket-line and winch motors to the driven 
pulleys with multiple V-belt drives. 

Power is taken on the dredge at 2400 volts and is stepped down 
by three 100-kva. transformers to 440 volts. A 5-kva. transformer is 
provided for lights. 

The dredge is operated 24 hours per day by one dredge-master, 
three winchmen, three oilers, two shore-men, one tractor driver, and 
one cleanup man. The direct operating cost is 4.3 cents per cubic yard 
to which should be added ^ cent per yard for management and ship- 
ment of bullion. No depreciation, no land-cost and no royalty are 
included. The capacity at Yreka is 140,000 cubic yards to 150,000 cubic 
yards per month. The same dredge would handle 210,000 cubic yards 
in easier ground. It cost approximately $160,000 including some mis- 
cellaneous pumping equipment for pumping muddy water out of the 



302 



pla(i:r AfiMxr, for ooi.d ix rAUFORxiA (Bull. 13.') 







Fig. ;tS. Steel luill •( .Ir. .Iui -r ^l.■l^:. i;,,ll li|.,l-;ii, 

<-(lli/„r,ii,t .Jo„,.,ul ui Mi.n.s ,i„,t (...,l..,ni. .1/' 




f-. 



ihl<n-,n<t .luunnil ,,i )/,„.x a,../ <:, ,,t. ,,,,,, A,,,, I i ■' : s , ,, , 



Sec. IV] MINES RY COUNTIES 303 

poiul, but not iiu'liidiufi' tlio ilf)-!!)). Cntcrj^iJliir tractor with diesel cMif^ine 
and bulldozer. 

Yuha Consolidated Gold Fields (Siskiyou Unit), 351 California 
Street, San Francisco, was the leadin<^ gohl producer in Siskiyou County 
in 1940. The company operated a Yuba type connected-bucket dredge 
with 72 buckets of !)-cu.ft. capacity near Callahan. The operation was 
continued throughout 1941. 

The following description of the dredge is reprinted from the Cali- 
fornia Journal of Mines and (ieology " foi- April, 1938: 

Yuba Consolidated (lold Fields built a new dredge near Callahan, 
Siskiyou County, in 1936, in sec. 8, T. 40 N., R. 8 W., M.D. P'rom a point 
near the confluence of Wildcat Creek and Scott River, it will work for 
sev'eral miles up the river. F. C. Van Deinse, 351 California Street, 
San Francisco, is vice-president and general manager. H. C. Perring 
is field-superintendent. 

The dredge is No. 116 of Yuba Manufacturing Company, and is built 
on a steel hull not of the pontoon type, 122 feet 8 inches by 56 feet by 
10 feet. It will now dig to a depth of 35 feet below water line, but is 
designed so that extensions can be put on both the hull and the digging- 
ladder ; and it will then dig to a depth of 50 feet or 60 feet. To cope with 
very difficult digging, this dredge was equipped with machinery of sizes 
ordinarily used on dredges with 18-cu.ft. buckets, while its buckets are 
of 9-cu.ft. size. Concentric ladder suspension is used, that is the ladder 
and the bucket-chain turn on the same axis. 

Gravel is screened in a trommel 8 feet in diameter by 48 feet long, 
of which 34 feet are perforated with |-inch to f -inch and f -inch to ^-inch 
holes. It turns at 7 rpm. The trommel is lined with f-inch plates of 
"abrasion resisting steel," a high-carbon, high-manganese steel supplied 
by United States Steel Corporation. It costs more per pound than 
ordinary steels but less per cubic yard dredged. Undersize from the 
trommel is treated on 3500 square feet of riffle-tables in a double-deck 
arrangement. They are provided with wooden riffles shod with steel. For 
washing, 10,000 gallons per minute of water are pumped from the pond. 
The total connected load is 750 hp., which includes an extra-heavy digging 
motor about midway in size between those customarily used in 18-cu.ft. 
dredges and 9-cu.ft. dredges. 

The dredge is operated for 24 hours per day by a total crew of 
24 men including a man in the office. The actual capacity is 210,000 
cubic yards per month in ground that is hard to dig. 

« Averill, C. V., op. cit. 



304 rLAf-KR MININO I'OU COLT) IN' CAr,II'()KNIA [RiilLlHr) 

STANISLAUS COUNTY 

(\{ K Prrdfjinn ('oniixnni, 1002 Pacific I'.uildin^'. I'ort land. Orcj^oii, 
op<M-at('(l a (Irajrliiie di-cd^'c with excavatoi- liaviii^' a 1 i-cu.yd. bucket on 
Littlejolm Crceiv two miles iioctliwest of Kni^dits l-'erry inteniiitteiitly 
between ScpteiidxT 20 and December 17, 11)40. The same ecpiipment was 
ti.sed in dredfi-injr the ad.)oinin<r -lack Welsii Uancli. 

Cnlifoniid Hold Dr(<hjiii<j Coin pahif. ;{')1 Califoi-nia Street. San 
Fi'ancisco. operated a eonnected-bncket dred^re in the .Jenn>- Lind dis- 
triet on tlie Stanislaus side of tlie connly line diii-inj; 1!)40. 

(icrmuiii, A. (!., o])erated a dra<;line dred<re nsinj? a .l-cu.yd. bneket 
in tlie Knijrhts Ferry district intermittently t'l-om .Inly 1.") to December 
28, lf)4:i The wasliin;.'- of (iof) cnbic yards of <rravel yielded 12 ounces of 
{joJd and 1 onnce of silver. The e(pii{)ment was desi<rne(l to be handled 
by one workman. 

La (Irauijc Hold Drcdf/iiuf CoHipniiji, IHOf) Mills linildiiifr. San Fran- 
cisco, oi)erated a eonnected-bncket dre(l<i:e on the Tnohnnne River in tlie 
La C}ran<j:edist]-ict throu<.diont l!)40and 1!)41. The dredjre was e<piipped 
with ()2 l)nckets of l()-c\i.ft. capacity. 

Placer J'roixrtics Coiiipaiiif, liox y>'.V2, Oakdale, <)i)eiate(l a di-a<iline 
dred^^e on the Stanislaus River nine miles east of Oakdale thi-onjjhout 
lf)40. A ()!- and a 7i-cn.yd. bucket were tried on a o-cn.yd. drajrline 
excavator at various times dni-in<i' the yeai'. The washin<i- plant used a 
shakinjr screen in l)lace of a trommel. In 1!>41 operations were continued 
with a ()-(Mi.yd. bucket at a point eijiht miles east of Oakdale. In 11U2 
operations were continued (lni"in<r most of the year with two di-ajjfline 
excavatoi-s. one with a H-cu.yd. bucket and the otiiei- with a 2.',-cu.yd. 
bucket. Operations were continued until I)ecend)er 12, l!(4.'i. 

Tuolkniiic (iold l)rrd(fin(/ Cftvporaiio)!, 1 Mont^romery Street, San 
Francisco, operated a connected-bucket dred}ie from February 22, 1!)40 
until Ai)ril l."{, li)41, when the (lred<:e capsized. It was c(piipped with 
100 buckets of 12-cu.ft. capacit.v. ( )p('rati()ns were cai-ricd on throughout 
li)43 (Ml a one-shift basis. 

Vanvicl, C. F., Route 2, Oakdale, oi)erated a drajrline dredge, employ- 
in{r an excavator with a 1. l-cu.yd. bucket on the Anderson, Ili;r^inbothani. 
and Kaasa pi'operty in the Knijihts Kerry disti-ict from May 1'\ until 
December 1:^. lf)41. The yield from ()2H.400 cubic yards of <rravel was 
2.1})H ounces of <rold and 17!) ounces of silvei-. 

Yiiha Consolidated Oo'd Fields, :{.")1 ("alifornia Sti-eet, San Fran- 
cisco, started operations with a connected-bucket di-cd;.:!'. electrically 
driven, in the La (!ran<re district on December 1."). 1!)41. 



Sec. IV] MINES BY COUNTIES 305 

TRINITY COUNTY 

The mineral resources of Trinity County have been described in 
the California Journal of Mines and Geology for January, 1941.^ 
Further details about many of the placer mines mentioned below are 
contained in this report, as well as descriptions of lode mines and of 
mineral deposits other than gold. The report contains a long table of 
mines with references to earlier reports. 

Arhuckle mine is a hydraulic mine near Weaverville that was oper- 
ated by Arbuekle Bros, of Weaverville durfng 3 months of 1940. 

B. H. K. Mines, Box 325, Orland, operated a dragline dredge 
equipped with a l|-cu.yd. bucket on Littlejohn Creek in the "Weaverville 
district from July 1 to the end of 1940. The yield from 184,000 cubic 
yards of gravel was 789 ounces of gold and 40 ounces of silver. In 1941 
operations were continued on Little Browns Creek at several properties 
with the following results : at the Rehberger property operations from 
January 1 to May 2 yielded 751 ounces of gold and 41 ounces of silver 
from 176,000 cubic yards of gravel ; at the M. K. Brown property opera- 
tions from May 3 to July 1 yielded 405 ounces of gold and 24 ounces of 
silver from 95,000 cubic yards of gravel ; at the Scharr property opera- 
tions from July 20 to September 12 yielded 349 ounces of gold and 28 
ounces of silver from 81,500 cubic yards of gravel ; and at the Tye prop- 
erty operations from September 13 to October 22 yielded 150 ounces of 
gold and 10 ounces of silver from 55,000 cubic yards of gravel. 

0. R. Batham, Box 325, Concord, operated a dragline dredge on the 
Bazet Estate property on the East Fork of Stuarts Fork from August 
10, 1941 to the end of the year. The recovery from 205,550 cubic yards 
of gravel was 626 ounces of gold and 50 ounces of silver. Batham also 
carried on smaller operations at the Hook and Ladder and Nugget Bar 
properties. 

/. P. Brennan, 1343 Butte Street, Redding, operated a dragline 
dredge using a f-cu.yd. bucket on Brown's Creek in the Weaverville 
district from July 17 to December 31, 1941. 

Canyon Placers on Canyon Creek was worked by the hydraulic 
method by G. H. Bergin of Junction City in 1940 and 1941. More than 
a page of additional information about this property is contained in 
California Journal of Mines and Geology for January, 1941.^ 

Carrville Gold Company, 351 California Street, San Francisco, or 
807 Lonsdale Building, Duluth, Minnesota, operated its dredge on the 
Trinity River about 3 miles north of Trinity Center throughout 1940 
and 1941. Operations were conducted through the company's agent, 
Yuba Consolidated Gold Fields. The connected-bucket dredge has 75 
buckets of 12-cu.ft. capacity. 

Cinco Mineros Company, First National Bank Building, Oroville, 
operated a dragline dredge using a 1^-cu.yd. bucket near Hayfork 
throughout 1940. The operation was continued in 1941 on the Albiez, 
Crews, Parmenter, Ross, and Trimble properties. 

1 Averlll, C. V., Mineral resources of Trinity County ; California Jour. Mines and 
Geology, vol. 37, pp. 8-89, 19 41. 

" Averlll, C. v., op. clt., pp. 29-30. 



20 



306 



PLACKR MININO FOR OOI.D IN CALIFORNIA [BuU. 135 




Fio. 100. Goldfield Coiisolidutt d Mmcs Company, hydraulic mino. /.'.;) 
California Journal uj Mines and Geology, January 191,1. p. o7. 




Fi(5. 101. DredKe of Junction City Mining Company. Keprinted from California 
Journal of Mines and Geology, Jannary 193S, j)- '■'7. 



Sec. IV] MINES BY COUNTIES 307 

Dobbin Gulch Drcdcjing Company of Redding operated a dragline 
dredge equipped witli a l]-('U.yd. bucl^et on the M. A. Brady property in 
the Weavorville district from June 18 to December 24, 1941. The yield 
from 213,800 cubic yards of gravel was 926 ounces of gold and 80 ounces 
of silver. In 1942 operations at the Brady property and the Sunshine 
mine were conducted from January 3 to October 19. At the Sunshine 
mine 107,300 cubic yards of gravel yielded 348 ounces of gold and 33 
ounces of silver. 

Golden Gravels Mining Company of Junction City operated at the 
Red Hill mine of Goldfield Consolidated Mines, near Junction City in 
1941. 

Goldfield Consolidated Mines, 1 Montgomery Street, San Francisco, 
operated its Red Hill hydraulic mine near Junction City in 1941 and 
jH-oduced a substantial quantity of gold. The mine was also operated 
during 1943. 

Havilah Gravels, Inc. of Lewiston operated a dragline dredge which 
had an excavator with a 2-cu.yd. bucket on Eastman Gulch from 
November 23 to December 31, 1941. The yield from 7860 cubic yards 
of gravel was 338 ounces of gold and 48 ounces of silver. A nonfloating 
washing plant operated by J. W. Martin and R. W. Setzer on the same 
property from January 1 to August 1, 1941, recovered 163 ounces of 
gold and 19 ounces of silver from 20,000 cubic yards of gravel. 

Interstate Mines, Inc., Box 14, Weaverville, operated a dragline 
dredge on the Lowden Ranch from January 4 to July 14, 1940. 

Junction City Mining Company, 685 Sixth Street, San Francisco, 
operated a connected-bucket dredge near Junction City in 1940, 1941, 
and until October 28, 1942. In 1942 the yield from 2,077,000 cubic 
yards of gravel was 7878 ounces of gold and 735 ounces of silver. The 
following additional details about this dredge are reprinted from the 
California Journal of Mines and Geology for January 1941.^ 

Junction City Mining Company started a modern steel bucket- 
ladder dredge in sec. 18 and adjoining sections, T. 33 N., R. 10 W., M. D., 
near Junction City, on January 10, 1936, and has been operating con- 
tinuously since that time. The company controls 8 miles of the river, 
the lower (northerly) end of the property' being in sec. 1, T. 33 N., R. 11 
W. Harvey Sorensen, 685 Sixth Street, San Francisco, is president ; 

C. M. Derby, Mills Tower, San Francisco, is consulting engineer; and 

D. B. Wilson is superintendent at Junction City. 

The hull of the dredge is new and of the late pontoon design, being 
no. 113 of Yuba ^Manufacturing Company. Transportation over moun- 
tain roads was one reason for adopting this design. The hull is 120 feet 
long by 52 feet wide by 8 feet 1 inch deep, and is made of 31 pontoons. 
These are designed and arranged so that the inside walls strengthen the 
hull at critical points. The largest pontoon weighs 24,000 pounds and 
the smallest 4800 pounds. Most of them weigh from 10,000 to 16,000 
pounds. When assembled they form a rigid structure owing to the 
beam-effect of the side-walls. Some of the machinery from the old 
Madrona dredge was used. 

3 Averill, C. V., op. cit., pp. 40-42. 



308 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

Tlie biK'ket-chaiii contains 7!) buckets of 9i-cu.ft. capacity each, and 
the dredge is capable of digging to a depth of 45 feet below waterline. 
A maximum depth of 58 feet has been reached by carrying part of the 
gravel as bank. Average depth of dredging is 28 feet. Bedrock varies 
from soft to hard but Ls decomposed enough so that a few inches of it can 
be taken up. The dredge is held in digging position by a single spud 
of 32 tons. The trommel is 7 feet in diameter and is perforated with 
•J-inch to ^-inch holes, but one section of 2-inch mesh is provided for 
recovery of nuggets. Riffles are of the Hungarian dredge type shod on 
top with ^-inch strap iron. The stacker for coarse tailing is 135 feet long 
and carries a 36-inch belt. The operating crew averages 24 men. 

Electric motors are as follows: 50 hp. on a high-pressure 10-inch 
pump, 50 hp. oil a low-pressure 10-inch pump, 50 hp. on an auxiliary 
10-inch pump, 25 hp. on a 4-inch pump, 35 hp. on the winch, 35 hp. on 
the screen, 50 hp. on the stacker, and a 200-lip. digging motor. 

The following figures on operation are furnished through the 
courtesy of C. M. Derby, consulting engineer. For the fiscal year ending 
June, 1937, the operating cost under rather severe conditions averaged 
4.98 cents per cubic j'ard. This includes labor, material, power, ordinary 
taxes, and general expense. No land-cost, no royalty, and no deprecia- 
tion are included. The average monthly yardage was 240,000 cubic 
yards. The approximate cost of the dredge was $250,000. 

When the dredge was operated near the old Chapman mine, recovery 
of platinum group metals was as high as 2 ounces per week, and pieces 
weighing as much as half an ounce were recovered. In other locations 
the recovery was about one-half ounce per week. Analysis of a shipment 
follows: waste or sand, 38% ; gold, 1.89% ; platinum, 25.78% ; iridium, 
10.51%; osmium, 16.21%; ruthenium, 7.71%; palladium, 0.27%. 
Recovery of platinum from sands removed from the riffles at time of 
clean-up is made on a long tom on the dredge. The last cleaning is done 
by panning ; and before the last panning, the concentrate is ground in a 
small ball mill and then is allowed to stand over night in nitric acid. 
Among the minerals contained in the concentrate is native cinnabar. 
The richest sand Is found, and the poorest recovei-y is made in passing 
through ground that has already been mined. The channel of the river 
was mined shortly after 1850 in the days of the gold-rush. A dime that 
looked new, which carried the date 1838, was recently recovered. 

C. L. Kalhangh, operated a suction dredge and tractor on the Thurs- 
day No. 1 mine on Crow Creek from May 1 to September 15, 1942. The 
yield from 1000 cubic yards of gravel was 103 ounces of gold. 

La Grange Placer Mines, Ltd., Box 141, Weaverville, operated its 
hydraulic mine between Junction City and Weaverville during parts of 
1940, 1941, and 1942. In 1941 operations lasted from January 1 to 
July 1 and from December 16 to 31. The yield from 113,100 cubic yards 
of gravel was 757 ounces of gold and 84 ounces of silver. Operations 
conducted from January 1 to July 1, 1942, yielded 548 ounces of gold 
and 52 ounces of silver from 250,000 cubic yards of gravel. 

Lcwiston Placers of Lewiston operated its hydraulic mine near 
Lewiston from January 27 to July 1 and from December 6 to 31, 1941. 
In 1942 operations from January 1 to June 30 yielded 188 ounces of 
gold and 24 ounces of silver from 75,000 cubic yards of gravel. 



Sec. IV 



:MIXES HY tOUNTIEP 



309 




102. Lincoln Gold Dredging Company, dragline dredge. Reprinted from CaU- 
foruia Journal of Mines and Geology, January lO',!, p. ',6. 



Lincoln Gold Bvcdoing Conipani/ of Lincoln operated dragline 
dredges in the Lewiston district in 1941 with the following results : 
from the Clark-Jansen property the yield from 109,139 cubic yards of 
gravel was 430 ounces of gold and 67 ounces of silver ; from the Costa 
property the yield from 26,432 cubic yards of gravel was 134 ounces of 
gold and 9 ounces of silver; from the Dickerson property the yield from 
65,856 cubic yards of gravel was 149 ounces of gold and 16 ounces of 
silver; from the Fancelli property the yield from 28,170 cubic yards of 
gravel Avas 141 ounces of gold and 19 ounces of silver ; from the Froloff 
property the yield from 562,732 cubic ^ards of gravel was 2453 ounces 
of gold and 158 ounces of silver ; and from the Phillips property the 
yield from 194.876 cubic yards of gravel was 1134 ounces of gold and 
']61 ounces of silver. One of the dragline excavators was equipped with 
a 2i-eu.yd. bucket and the other with a 1^-cu.yd. bucket. In addition 
to this production from dragline operations small amounts of gold and 
silver were recovered by hydraulic operations at the Costa and Phillips 
properties. 

In 1942 operations were continued from January 1 to Septem- 
ber 12 on the Costa property on Hush Creek with a dragline excavator 
having a 22-cu.yd. bucket. The yield from 271,744 cubic yards of 
gravel was 1406 ounces of gold and 95 ounces of silver. 

As this dredge has several features that are different in design 
from those commonly used, the following description is reprinted from 
the California Journal of Mines and Geology for January 1941^: 

Lincoln Gold Dredging Company is a partnership of E. M. Clark, 
French Gulch, and W. K. Jensen, Lincoln, California. Late in 1939, 
a dragline dredge was installed on a tract of 60 acres held by leases, 
coA'ering bars on Trinity River, at a point 4 miles west of Lewiston, 
in sec. 27( ?), T. 33 N., R. 9 W., M. D. It was planned to dredge this 

* Averill, C. V., op. cit., pp. 45-47. 



310 PLACER MINING FOR GOLD IN CALIFORNIA [BuU. 135 

tract to a depth of 6 feet to 23 feet. The washing-plant is similar to 
those made by Bodinson, which have been described in some detail in 
a preceding chapter, but it is of Clark's own make. It has a capacity 
of 3500 cubic yards per day, and is driven by a D-13000 Caterpillar 
diesel engine. A 25-kw. electric generator is provided for lights and 
for one or two small motors as needed. Main drive is from engine to 
countershaft by multiple V-belt. 

Several improvements on older designs have been incorporated. 
Disc-wheels, 3f) inches in diameter, are attached to hand-winches instead 
of cranks. This is a safety measure to prevent the breaking of the 
operator's arm by a sudden strain which might reverse the direction 
of rotation of the crank. Beneath the trommel is the usual depressed 
trough containing baffles to regulate the flow of sand and water to each 
sluice. In each compartment of this, beneath the surface of the fluid, 
a jet of water supplied from a manifold impinges against a horizontal 
plate. Thus the contents of each compartment are kept in a state of 
agitation, giving the gold a chance to settle out. Clark says that most 
of his gold is recovered in these traps, and that it is not necessary to 
clean up the sluices so often. Sluices are equipped entirely with 
expanded metal lath over coconut matting, no riffles. Near the trommel 
a few strips of plate for amalgamation (silvered copper), 1| inches 
wide and as long as the width of the sluice, are placed beneath the 
expanded metal lath. The pump-screen is in the form of a revolving 
drum to keep it free of floating trash. Several gates made of heavy 
steel bars, placed above the tailing stacker, are arranged to open 
upward only. Boulders traveling up the belt in the normal way pass 
through readily; but if a round boulder starts to roll back down the 
belt, it is stopped by one of the gates, and is given a Tiew start in the 
proper direction. The dragline is a model 85 Northwest with a bucket 
of 2-cu.yd. capacity. The outfit includes also a Caterpillar tractor 
equipped with bulldozer. 

North Fork Placer Mining Company of Helena operated the North 
Fork hydraulic mine 1 mile from Helena from January 1 to June 30, 
1941. The recovery from 53,500 cubic yards of gravel was 277 ounces 
of gold and 30 ounces of silver. Operations at this mine in 1939 are 
described in the California Journal of Mines and Geology"^ for January 
1941. The following description of an earlier period of operation is 
from Gardner and Johnson ^ : The North Fork placers on Trinity River 
at Helena were worked under a leasehold during the 1932 season by 
F. M. Reynolds, W. 0. Kunman, and E. C. Mathews. A fourth man 
was employed. The mine was operated two 9-hour shifts with two 
men on a shift. The gravel deposit consisted of an old channel cutting 
through a ridge. The lower 15 feet of gravel was very tight and partly 
cemented. It was broken down by first cutting the bedrock from 
underneath it. After being broken down considerable piping was 
necessary to disintegrate the cemented fragments. The top gravel 
washed easily. 

"Water was brought to the mine from two sources in different flume 
lines. The lower flume emptied into a reservoir which supplied a giant 

» Averill. C. V.. op. cit., pp. 52-53. 

•Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, 
Part II, Hydraulicklng, etc. : U.S. Bur. Mines Inf. Circ. 6787, p. S.l, 1934. 



Sec. IV] MIN'KS I'.Y COUXTIKS 311 

■\vitli a r)-iiicli no/./.li' tor a])()iit .") lioiii's' pipiii;^^ a (lay. A pipe line to 
tlic upjKn- flume supplied one f^iant witti a 7-iiieli nozzle steadily. Two 
had l)i-eaks in tlie Jinnies dui-in<i' tlie season material 1\- inereased the cost 
])er enhic yard washed. As the walei- supi)ly decreased the diameters 
of tlie noz/les were reduced from 7 to (5 inches and fiiudly to f) inches. 

Two sluices, consistinji- of seven I'i-foot boxes 48 inches wide were 
used. One sluice emptied out of one end of the pit throu<ih a bedrock 
cut varyin<i: up to 30 feet in depth ; the other box went out the ()ii])osite 
end. The riffles consisted of heavy rails placed crosswise in the boxes 
on top of 4- by 4-inch timber. An undercurrent was used at the end of 
the sluice that carried away most of the material. The undercurrent 
table was 12 by 20 feet and was decked with the type of Hungarian 
I'ifilles used on dred^'cs. Between 800 and 1,000 cubic yards was handled 
in 18 hours with a full head of water. The averaj^e daily yardage handled 
for the season Avas 770 cubic yards. One hundred and fifty thousand 
cubic yards Avas washed during the season (December 15 to June 30). 
The labor cost was 3 cents per cubic j'ard ; supplies were estimated at 
] ] cents, making a total operating cost of 4i cents. The lessees had no 
supei'vision or {general costs. The indicated costs do not include deprecia- 
tion, interest on investment, or amortization. 

Oro Trinify Dredging Company, Box 212, Oroville, operated a diesel- 
]iowered dragline dredge equipped with excavator using a 1^-cu.yd. 
bucket near Weaverville from January 1 to June 18, 1940. The equip- 
ment then was moved to the Scott River district, Siskiyou County, where 
operatioTis were resumed on August 10. 

Placer Exploration Company. See Viking Dredging Company. 

Red Hill mine is one of the mines operated by Goldfield Consolidated 
Mines Company and is mentioned above under that heading. 

Beddings Creek Placer, Ltd., installed new equipment at the AVallace 
Bros, mine in sec. 33, T. 32 N., R. 9 W., M.D. The operation is of interest 
because a Ruble elevator Avas used. It was described in the California 
Journal of Klines and Geology "' for January-April, 1933, but this is 
out of print. The following description is from Gardner and Johnson :^ 
Placer operations on Redding Creek near Douglas City were begun in the 
spring of 1932 ; 56,600 cubic yards of gravel was washed by the time 
the water supply failed. The gravel bed, which was 9 feet deep and 120 
feet Avide, lay in a creek bottom. The fall of the creek Avas so slight (one- 
tenth inch to the foot) that enough grade could not be obtained for sluice 
boxes. A Ruble elcA'ator Avas used for elevating the gravel and boulders 
and sorting out everything over 2 inches in diameter. Water under a 
300-foot head Avas brought to the pit through a 24-inch pipe 3,000 feet 
long. The Y's in the pit Avere of 15-inch pipe. The gravel AA^as cut and 
sAvept to near the entrance of the Ruble by a giant Avith a 5- or 6-inch 
nozzle, then the material Avas Avashed up the Ruble by means of a second 
giant Avith a 5-inch nozzle. A third giant Avith a 3-inch nozzle Avas used 
intermittently to level off the tailings piles. 

The Ruble Avas 8 feet Avide by 60 feet long and elevated the oversize 
25 feet. It AA-as lined Avith sheet steel. The grizzlies were of 3- by 6-inch 
timber set on edge ; the top edge Avas steel-clad. They Avere placed cross- 
Avise on 3- by 6-inch sills laid lengthwise on the sheet-iron bottom of the 

^ Averill, C. V., Gold deposits of the Redding and AVcaverville quadrangles : Cali- 
fornia .Tour. Mines and Geology, vol. 29, pp. 68-69, 1933. 
8 Op. cit. 



312 



PLACER MINING FOR fiOLD IN CALIFORNIA 



[Bull. 135 




>-'V.- 



^i:: 



■^•i'. ^^ 



F:g. lO.T. Weaver Dredging Company, dragline dredge. A'-; ^ CdUforma 

JonriKil of Mines and Geolofiy, January 19', 1, p. Hi. 

chute. Tlie plus 2-in('li material was washed up through the elevator by 
the giant ; the undersize dropped through the grizzly and ran down the 
bottom of the chute to four 12-foot boxes, 48 inches wide, set at right 
angles to the elevator. As the gravel was only 9 feet deep, the Ruble had 
to be moved three times during the season. With 7 men and a Caterpillar 
tractor a week was re(iuired to move the elevator to a new location. A 
second elevator was planned next season to allow continuous production. 
Boulders were bulldozed; 2,000 pounds of 40-percent-strength gelatin 
dynamite was u.sed for this purpose during the 1932 season. An average 
of 540 cubic yards per day was washed during the 1932 season. The 
operating cost of washing the gravel was 19 cents, of which three-fourths 
was for labor. The co.st did not include ditch work (other than the ditch 
tender), construction costs, interest, depreciation, or amortization. 

//. S. Smith, R. A. Synith, and R. I. Smith, operated a dragline 
dredge using a 3-cu.yd. bucket on the High Channel mine in the Hayfork 
district for 30 days in August and September, 1941. The yield from 
100,000 cubic yards of gravel was 300 ounces of gold and 40 ounces of 
silver. In addition, a small quantity of gold was recovered at this prop- 
erty by hydraulic mining. 

Swanson Mining Corporation of Salyer hydraulicked a small yardage 
of very high-grade gravel at the Salyer mine between February 9 and 
May 24, 1940. Operations were continued in 1941. Further details 
about this property are given under two headings. Salyer Consolidated 
Mines Company and Swanson Mining Corporation in the California 
Journal of Mines and Geology for January. 1941.^ At this mine one 
ounce of platinum-group metals was recovered for each 20 ounces of gold 
and an analysis of this is given in the publication cited. 

Trinifxj Dredge was operated on the Trinity River at a point about 
4 miles north of Lowiston by C. R. and T. D. Harris of Lewiston from 



» Averill, C. V.. op. cit.. pp. 59-62. 



Sec. IV] MINES BY COUNTIES 313 

January 1 to November 15, 1940, when the deposit was exhausted. This 
dredge is described in the California Journal of Mines and Geology for 
January, 1941.^0 

Viking Dredging Company, Box 498, Chico, operated a dragline 
dredge equipped with a 2-cu.yd. bucket throughout 1940 on Filibuster 
Flat, Shanahan Bar, and Hidden Channel near the confluence of Redding 
Creek and Trinity River. The company operated the Hidden Channel, 
Tout, and Gasper properties in the Weaverville district from January 1 
to February 28, 1941. Then the operation and equipment were taken 
over by Placer Exploration Company of Douglas City, which continued 
operations until December 2. The dragline dredge was equipped with 
a 2-cu.yd bucket. 

Weaver Dredging Company, Box 216, Weaverville, operated a drag- 
line dredge using a 1-cu.yd. bucket on East Weaver Creek from January 
1 to June 12, 1940. Then the equipment was shipped to Montana. The 
company operated a second dragline dredge equipped with a 2^-cu.yd. 
bucket on La Grange property during parts of 1940. This operation was 
continued from January 1 to May 19, 1941, and the yield from 231,124 
cubic yards of gravel was 976 ounces of gold and 89 ounces of silver. 

W. E. Woodbury, hydraulicked 20,000 cubic yards of gravel at the 
Rex mine east of Weaver Creek, near Weaverville, during 1941. 

TUOLUMNE COUNTY 

Barker Corporation, Hornitos, operated a dragline dredge on Tuol- 
umne River near Jacksonville from January 1 until November 18, 1940. 
Then the equipment was moved to Hornitos, Mariposa County. 

Jackass property in the East Belt district was worked by L. R. 
Harris of Merced with a dragline dredge from April 20 to May 22, 1940. 

E. A. Kent, 260 California Street, San Francisco, operated a drag- 
line dredge with a If-cu.yd. bucket on Six Bit Gulch near Chinese Camp 
in December 1940. A second dragline dredge equipped with a 2i-cu.yd. 
bucket was operated on Sanguinetti Ridge near Chinese Camp from June 
29 until the end of 1940. Operations with these two dredges were con- 
tinued in 1941 on the two properties mentioned above and on the Rosasco 
property. In 1942 operations with the two dredges were continued 
from January 2 to February 19 with the following results : on the Lyons 
Ranch 53,000 cubic yards of gravel yielded 224 ounces of gold and 15 
ounces of silver; on the Rosasco Ranch 52,500 cubic yards of gravel 
yielded 308 ounces of gold and 21 ounces of silver. 

La Bienvenita mine was operated during 1940 by E, Z, Bowman, 
Box 6, Chinese Camp, who used a nonfloating washing plant. 

Menke-Hess property near Chinese Camp was operated in 1941 by 
Rio Development Company and' McMillan & Company of Jamestown, 
who used a nonfloating washing plant. 

Mullin & Company, Sonora, washed 55,700 cubic yards of gravel 
by dragline dredge on Sullivan Creek in 1940 and recovered 419 ounces 
of gold and 41 ounces of silver. 

Mullin-Ilampton Dredging Company of Sonora operated a dragline 
dredge which had an excavator with 1^-cu.yd. bucket on the Kaplan 

>» Averill, C. V., op. cit.. pp. 62-63. 



314 



PLACER MIXING FOR OOLD IX CALIFORNIA 



Bull. 135 




Sec. IV] MINES BY COUNTIES 315 

(Dondero) mine on Woods Creek 1 mile east of Columbia from January 
29 to July 15, 1941. The yield from 85,000 cubic yards of gravel was 
365 ounces of gold and 28 ounces of silver. 

H. M. Richards did ground .sluicing at Ohio Flat in the Challenge 
district and recovered 23 ounces of gold from 1000 cubic yards of gravel 
between January 1 and April 15, 1943. 

YUBA COUNTY 

Arundel Corporation, Box 951, Marysville, produced a substantial 
quantity of gold in the Smartsville district in 1940 in preparing gravel 
for concrete aggregate. 

Dove Mining Company, Oregonhouse, operated a nonfloating wash- 
ing plant on the Rose property in 1941. 

Parks Bar Company, Box 932, Nevada City, operated a diesel- 
powered dragline dredge equipped with a l^-cu.yd. bucket in Big Ravine 
in the Smartsville district from May 1 to October 31, 1940. The recovery 
from 95,000 cubic yards of gravel was 429 ounces of gold and 20 ounces 
of silver. 

R. & M. Mining Company of La Porte operated a dragline dredge 
using an excavator with a l^-cu.yd. bucket at several properties on Slate 
Creek in the Strawberry Valley district in 1940 and 1941. In 1940 the 
Corley and Princess Pines properties were worked. In 1941 the Corley 
property yielded 423 ounces of gold and 36 ounces of silver from 134,000 
cubic yards of gravel between April 15 and June 21 ; the Ophir property 
yielded 76 ounces of gold and 7 ounces of silver from 15,000 cubic yards 
of gravel between June 21 and July 8 ; and the First Chance property 
yielded 691 ounces of gold and 60 ounces of silver from 99,000 cubic 
yards of gravel between July 21 and November 27. 

Sunmar Dredging Company, Box 228, Oroville, operated a dragline 
dredge on property of Mammoth Mining Company in the Smartsville 
district during 1940. The dragline excavator had a 2-cu.yd. bucket. 

Williams Bar Dredging Company, 232 Montgomery Street, San 
Francisco, or Box 575, Marysville, operated a connected-bucket dredge 
on the Yuba River 4 miles northwest of Smartsville throughout 1940, 
1941, and 1942. The operation was suspended January 13, 1943, under 
Limitation Order L-208 of the War Production Board. The dredge was 
equipped with 84 buckets of 6-cu.ft. capacity. In 1942 the yield from 
2,872,327 cubic yards of gravel was 6,354 ounces of gold and 447 ounces 
of silver, 

Yuha Consolidated Goldfields, 351 California Street, San Francisco, 
operated a fleet of six dredges at its property in the Yuba River basin 
near Hammonton in 1941. All the dredges were equipped with 18-cu.ft. 
buckets and electric power. Two had 87 buckets each; two had 100 
buckets each ; one had 126 buckets ; one had 135 buckets. In 1943 the 
company was allowed to operate two of the dredges, the one with 126 
buckets and the one with 135 buckets. 

The following article. Deep Gravels Dredged Successfidly, describes 
one of these dredges. 



316 



PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 




DEEP GRAVELS DREDGED SUCCESSFULLY 

By Herbert Sawin • 

Modern dredges, as operated by Yuba Consolidated Gold Fields, 
overcome obstacles today that seemed insurmountable only a few years 
ago. Early California dredge men considered a digging depth of 60 feet 
below water level the maximum range of economical bucket-line dredging. 
Later, owing to new designs and improved materials, 80 feet, then 112 
feet, and now 12-1 feet, below water level are profitable operating ranges. 
Based on experience with Yuba 17, a 3,500-ton gold dredge built-in 1934 
and operated at Hammonton, California, which dredged abrasive and 
tightly packed gravel at depths to 112 feet below water level, Yuba 20 
was designed and built for the same field, starting operations on May 1, 
1939. This newest addition to a fleet of six 18-cu.ft. dredges digs to a 
depth of 124 feet below water level, at times against a bank of 50 feet. 
The contract for Yuba 20 was signed August 4, 1938. The first hull plates 
were laid in November, and the hull was launched 30 days later. The 
job was completed, and the dredge operated its first full day, on May 1, 
1939. Considering the weight of 3,700 tons, the period of less than eleven 
months from contract date to starting of the dredge is noteworthy. 

Electrically operated and displacing about 3,700 tons, the steel hull, 
superstructure, and gantries of the dredge alone weigh 1,500 tons. The 
digging units weigh 860 tons exclusive of gravel and suspersion parts. 
Its steadiness in the water while digging is noticeable at once to a visitor 
acquainted with placer mining dredges. The hull measures 250 feet, 
8 inches by 80 feet by 11 feet. The digging ladder is 216 feet long and 
13 feet f inch deep ; the main stacker measures 225 feet between pulley 
centers, and carries a 44-inch rubber conveyor belt. With the ladder 
raised to 30 feet above water, over-all length of the dredge is about 540 
feet. These weights and dimensions clearly indicate the hug'e size of the 
dredge. Perhaps it is easier to visualize a dredge as long as an average 
citj' block and with its topmost point, the stern gantry, ten stories above 
the pond surface. 

Describing the dredge briefly from ' * stem to stern, ' ' principal parts 
include the following : 

1. Manganese-steel, two-piece lower tumbler with nickel-steel shaft. 

2. 135 manganese-steel, rivetless-lip buckets. 

3. Forged nickel-chromium steel bucket pins. 

4. One-piece cast high-carbon-chromium steel upper tumbler having 
shaft cast integral. 

5. Forged nickel-chromium steel tumbler wearing plates. 

6. Perry bucket idler mounted on under side of digging ladder. 

7. Bucket idler in well. 

8. Packed lower ladder suspension blocks. 

9. Cast-steel upper and lower block sheaves, 60-inch diameter. 

10. Ladder hoist lines, 2-inch wire rope. 

11. Monitor on bow to knock down high banks. 

* Sales Engineer, YuWa Manufacturing Company, San Francisco, California. This 
article was published in Engineering and Mining Journal, vol. 144, no. 7, for July 1943, 
and is reprinted by permission of that journal. 

(317) 



318 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

12. Kc'volviii^f screon 50 I'oet G indies Ion*? and 9 feet diameter, using 
4-incli Ynba A1{S seroeu plates, and ^vitll friction drive at lower end. 

13. Wincli room on the center line of the dredge with flying bridge 
extending to both sides. 

14. Two-drum hiddei- hoist winch on port side. 

15. Eight-drnm swing winch on starboard sick', having separate 
drums for each of the port and starboard bow lines. 

IG. Auxiliary stacker 48 feet long with 44-inch belt to carry over- 
size material from the screen to main stacker or to rock chutes. 

17. 'Main stacker about 18 degrees for normal work, but this can 
be changed as desii-ed. 

18. Double-drum sta<'ker hoist winch driven by a single motor with 
worm drives. 

li). Two spuds, box type. 37 inches by GO inches by 70 feet. 

20. Table ai-ca, G,000 s(piare feet, single-bank, double-decked with 
molded rubber liungarian-type rifilies. 

21. Hinged top deck sluices can be raised to clean up lower sluices. 

22. Tail sluices extending about 30 feet aft of stern. 

23. Auxiliary spill chute aft of screen, permitting rock tailings to 
be discharged through a well in the stern. 

24. Two sand wheels discharging to 30-inch belt conveyors which 
carry excess sand to the main stacker. 

25. Conveyor idlers, troughing and return, of the anti-friction type. 
Tumps include the following Yuba centrifugal units: one 14-inch, 

70-foot head, 5,500 gpm. ; one 14-inch, 52-foot head, 5,500 gpm. ; one 
6-inch dual, llG-foot head, 1,100 gpm.; one 4-inch auxiliary, G5-foot 
head, 450 gpm. ; and a 2-inch service pump. A Yuba mud removal 
system using an 8-inch Byron-Jackson pump rated at 3,000 gpm., 245- 
foot head, also fnrnishes water to the monitor mentioned previously. 
Total installed load is 2,175 hp., all a.c. power. 

Two variable-speed drive motors, each 300 h])., GOO rpm., are situated 
just aft of the upper tujnbler, one on each side, with V-belts connecting 
them to the pulley shaft. This arrangement was first tried on Capital 
No. 4 dredge, built in li)37, where the multiple a.c. motor drive has been 
entirely satisfactoi\v and resulting in a simple, trouble-free installation. 
The ladder winch is sei)arate from the nuun drive, thus eliminating the 
large belt formerh' needed. V-beit drives are also used on the swing 
winch, screen drive, and main and auxiliary stackers. 

The main drive on Ynba 20 has proved to be highly successful. At 
Ilammonton, about 00 feet below water level, there is a jnirticularly hard 
(but not cemented) gravel stratum. The drive in question helps materi- 
ally in solving dredging problems associated with digging hard formations 
at great depths. The double V-belt main drive provides a flexible unit 
which acts as a safety link capable of absorbing severe shocks and pro- 
tecting the rest of the digging unit in the event of sudden or severe over- 
load. Bucket line speed is 21 per minute, based on the experience of 
several deep digging dredges in California. 

In general, dredges digging 100 feet or more below water level have 
been found to excavate less material per day than units of the same bucket 
capacity digging at 80 feet or less. For example. Capital No. 4 dredge, 



Sec. IV] DEEP GRAVELS DREDGED SUCCESSFULLY — SAWIN 



319 



(li<?frin{? to 82 feet ^vitll 18-cii.ft. buckets, was capable of turning out 127,- 
000 cubic yards of gravel per week, but its most economical rate was set 
at 100.000 cubic yards. For Yuba Xo. 20, on the other hand, the greatest 
weekly yardage luis been about 00,000 cubic yards. Reasons for this 
are the longer time required on the larger dredge for unproductive opera- 
tions such as raising the ladder, oiling, stepping, and moving, and the 
less sensitive control the winchman on the larger dredge has over the 
actual digging. Because of the greater weight of tlie dredge, he is not 
con.scious of slight variations in digging depth as he would be on a smaller 
dredge, and it the buckets are not cutting deeply, several minutes will 
elapse before the half-empty buckets travel up into sight and the winch- 
man drops the ladder to a correct digging position. With the larger 
dredge digging is necessarily slower in corners or at other points where 
caving might cause serious accidents. A further factor in the yardage 
dug by Yuba No. 20 is the tight formation mentioned in the foregoing. 
Successful deep dredging owes much to the use of an idler to control 
the catenary of the bucket line in its return to the lower tumbler. A 
Perry pateiited idler, named for its inventor, 0. B. Perry, was first used 
on Yuba 17 at Ilammonton, California. Yuba 20 is also equipped with 
one. It is a cylindrical device, wheel-like in design, mounted on the 
underside of the digging ladder about midway between the tumblers. 
The buckets ride upside down over the idler, the contour of the face 
fitting the bucket lips. Renewable cast manganese-steel wearing plates 
are provided on the idler itself, and renewable forged nickel-cbromium 
steel wearing bars protect the steel suspension unit. Both wearing plates 
and bars show little wear after many months of use, and because the long 
bucket line is better balanced, wear on bucket pins, bushings, and tumbler 
plates is reduced noticeably. The Perry idlers on Yuba's 17 and 20 
make it possible to use buckets and bucket pins of the same design and 
metal sections as on shallower digging dredges in the same field, and 
buckets and pins are therefore interchangeable on all dredges in use in 
this field. 

The Yuba mud removal system, also a help in deep dredging, pro- 
vides suction behind the lower tumbler in the form of a pipe line inside 
the digging ladder with a flexible hose coupling to a pump on deck. On 
Yuba 20, a "Y" arrangement of gate valves permits discharge of mud 
pumped from the pond bottom either tlirough a pipe line carried by the 
main stacker to a point far beyond the face of the rock tailings, or by a 
floating pipe line away from the dredge to a point several thousand feet 
distant, where the mud can be used for filling old holes or basins. In 
these basins muddy water can settle and be filtered through tailing piles 
to avoid stream discoloration. The mud sometimes reaches a depth of 
30 feet on the bottom of the pond, crowding the lower tumbler and unless 
removed prevents free swinging of the dredge. 

Auxiliary stacking and other stern-end equipment also attract 
favorable attention of experienced dredge operators. A well is provided 
on the center line of the hull at the stern, through which rock tailings 
can be discharged to make anchorage for the spuds, a departure made 
desirable by the length of the dredge. This is believed to be the first 
dredge so built. Part of the sand tailings are discharged to the main 
stacker belt to aid in binding rock tailings. The stacker was first used 
at an elevation of 23 degrees, the high elevation being necessary during 



320 



PLACKR MININO FOR GOLD IX CALIFORNIA [Bull.l.Sr 




nii^*-"TTTTT 



1 



■*«'^n' 



See. IV] DEEP GRAVELS DREDGED SUCCESSFULLY — SAWIN 321 

early operations until tlie pond became deep enough to dispose of rock 
tailiiijrs witliout sucli hi^li stacking. 

Deep dredging methods miist be developed to suit conditions that 
are decidedly different fi'om those encountered in shallow dredging. An 
imi)()rtant change is in the design of the ladder hoist winch. On Yuba 
20, this unit is separated from the main drive and occupies a deck space 
measuring 29 by 14 feet on the port side of the deck just inside the house. 
The total weight of the wincli, including structural steel base, brake 
assembly, etc., is al)out 63 tons. The two ladder hoist lines are 2-inch 
wire rope on separate drums. licngth of each is 2,300 feet. Each drum 
weighs 12 tons, and is driven tlwough a pinion shaft which also carries 
the mechanical brake wheel. All shafts used on the winch assembly are 
nickel steel. 

Power is supplied by a ."jOO-lip., 1,160-rpm. type "CW" Westing- 
house motor e(|uiiiped with a Westinghouse Thrustor brake type HI-198, 
and operating through a Farrel speed reducer with a ratio of 7.181:1. 
All pinions and gears have herringbone cut teeth. The mechanical brake 
is of the post type, actuated by releasing pressure in a 10- by 10-inch 
Westinghouse air cylinder, counterweighted. Brakes are electrically 
operated and manually controlled from the pilot house. Manual control 
gives the winchman a finer "feel" and saves possible damage to equip- 
ment which might occur with full automatic brakes. The braking action, 
tiirough the brake wheel to the drive pinion-s, slows down and stops both 
drums simultaneously. Immediately following the mechanical brake 
action, the Thrustor brake on the motor is applied automatically. A 
Lilly control is provided as a safety measure. Should the ladder be 
i-aised or lowered beyond safe limits or accidentally be dropped too fast, 
this unit would take control out of the winchman 's hands and apply the 
brakes automatically. This type of control a.ssures a longer life for 
winch parts. Internal expanding type clutches are used and are oper- 
ated pneumatically from the pilot house. With drums revolving at a 
speed of 7.46 rpm., the raising and lowering speed for the digging ladder 
is about 12 vertical feet per minute at the lower tumbler. 

The swing winch on Yuba 20 is on the starboard side just inside the 
front end of the house. The bow-line drums can be operated inde- 
pendently of the other drums on the winch, and a separate drum is used 
for each of the bow starboard swing lines. Other drums on the winch 
include two stern-line drums, two spud-line drums, and two spares. 
Clutches on all the drums are of internal expanding type controlled 
electrically through pneumatic cylinders mounted on the wdnch frame. 
The application of air cylinders to dredge equipment was originally 
developed and patented by Yuba about ten years ago for use on dredges 
to be operated in the tropics. ^Manually operated brakes are provided 
fen- the same reason as used on the ladder hoist winch. The winchman 
has better control in applying them, thus avoiding shocks to lines and 
thereby increasing the life of the wire rope. 

TJie history of dredge mining proves that successful dredges are 
especially designed to suit conditions to be overcome in a particular field. 
There is practically no so-called "standard dredge." This applies in 
pai-ticular to deep-digging dredges, which present problems entirely dif- 
ferent from those connected with shallow dredging. Smaller yardage 
with a given size of bucket naturally reduces the gro.ss income. 



322 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

The initial biprh cost of a dredjro like Yuba 20 burdens the cost of 
operation, and properties sufTu-iently larjjre to eai-ry the load of such an 
investment are not found often. Meehanically, the limit in size for 
mining dredges has not been reached. P^conomie problems which affect 
the cost of dredging are the main factors limiting meciianical size at 
present. 

An 18-cu.ft. dredge in California digging 80 feet below water level 
operates at a field cost of less than 3 cents per cubic yard. Beyond 80- 
foot digging depth, the operating cost rises sharply, and for dredges 
digging 100 to 120 feet, the field cost is nearer to 5 cents per cubic yard. 
This rising cost must be given serious thought when considering a deej) 
dredging venture, one reason being that areas large enough and deep 
enough to warrant the investment, probably would not have a high aver- 
age value per yard. For profitable deep dredging, the maximum dredg- 
ing depth would be determined by an anticipated return commensurate 
with the extra operating costs. It is probable that mechanical improve- 
ments and changes will be developed which may result in dredges of 
larger daily capacities with a given size of bucket, and do so economically, 
making otherwise worthless ground valuable mining property. 

Operating data on Yuba 20 have been furnished by Yuba Con- 
solidated Gold Fields, and with thanks to tliat company the following 
information is made available: Daily operating time (three shifts) has 
averaged 21 hours and 29 minutes. This makes full allowance for shut- 
dowiLs for all reasons, including moving, ladder inspections, clean-uji, 
repairs, and greasing. Gravel dug has averaged 12,260 cubic j'ards per 
day at a field cost of 4.32 cents per cubic yard. The weekly power con- 
sumption has been about 145,000 kw.-hr. 

On page ')! of this bulletin the gold mining tables as installed origi- 
nally on Yuba Xo. 20 are deseribed. Kec-ent experience with Yuba Xo. 
20 in digging through old rock piles and underlying sand beds from 
older operations pointed to a jieriodie excess of sand and greater (|uanti- 
tics of fine gold. This condition was caused by concentrations from 
dredges operating in the same area at jirior times which could not dig 
as deep as Xo. 20. To meet tliis condition jigs were jirojiosed for use 
instead of i-iffles. Exiiaustive studies wei-e made to improve the recovery 
factor as a means of counteracting increased opei'ating expense. 

liefore installing jigs, however, a thoi-ougli test was conducted. The 
exti-emely high volume of sand enconntei-ed at times i)roduced ditficult 
material handling conditions for jigs. Yuba jigs used experimentally 
proved to be capable of efficient operation. A full set of jigs designed aiul 
built by Yuba Manufacturing Company was installed on Yuba Xo. 20 in 
late 1!)4(). The Yuba jig is of the horizontal thrust design with a small 
motor moinited between and operating two cells. The eccentric drives are 
com|)letely enclosed and run in oil with heavy roller bearings used to 
red\ice wear and to pi'ovide long operating life. Headroom recpiirenients 
are kept to a minimum because of the horizontal tlirusi and this feature 
is of gi-eat advantage under di-edge ojx'rating conditions. 

There are twelve 4-cell rougher jigs and two 4-cell cleaner jigs on 
Yuba Xo. 20 and the complete circuit includes a ball mill and a small area 
of liffles over which jig concentrates are run. The gold recovery factor 
has been imj)roved sufficiently to justify the change from riffles, even 
though an extra man per shift is needed to operate the jigs and auxiliai-y 
mechanical e(iuipnuMit installed on Yuba Xo. 20 to replace tables. 



APPENDIX 



LAWS AFFECTING PLACER MINING 

A few laws that apply particularly to placer mining are brought 
together here for ready reference from a number of different publica- 
tions. For detailed information on other phases of mining law, refer- 
ence should be made to Bulletin 123, American Mining Law'^, and 
Bulletin 127, Manner of Locating and Holding Mineral Claims in Cali- 
fornia.^ 

1 Ricketts, A. H., American mining law: California Div. Mines Bull. 123, pp. 
1-1018, 1943. 

2 Ricketts, A. H., Manner of locating and holding mineral claims in California 
(with forms) : California Div. Mines Bull. 127, pp. 1-35, with revisions by C. A. Logan, 
March 1944. 



THE CAMINETTI LAW 

An Act to create the Calif ornia Debris Commission and 
regulate hydraulic mining in the State of California. 

(Approved March 1, 1893.) 

Be it enacted by the Senate and House of Representatives of the 
United States of America in Congress assembled, That a commission is 
hereby created, to be known as the California Debris Commission, con- 
sisting of three members. The President of the United States shall, by 
and with the advice and consent of the Senate, appoint the commission 
from officers of the Corps of Engineers, United States Army. Vacan- 
cies occurring therein .shall be filled in like manner. It shall have the 
authority, and exercise the poAvers hereinafter set forth, under the 
supervision of the Chief of Engineers and direction of the Secretary 
of War. 

Sec. 2. That said commission shall organize within thirty days 
after its appointment by the selection of such officers as may be required 
in the performance of its duties, the same to be selected from the mem- 
bers thereof. The members of said commission shall receive no greater 
compensation than is now allowed by law to each, respectively, as an 
officer of said Corps of Engineers. It shall also adopt rules and regula- 
tions not inconsistent with law, to govern its deliberations and prescribe 
the method of procedure under the provisions of this Act. 

Sec. 3. That the jurisdiction of said commission, in so far as the 
same affects mining carried on by the hydraulic process, shall extend 
to all such mining in the territory drained by the Sacramento and 
San Joaquin river systems in the State of California. Hydraulic min- 
ing, as defined in section eight hereof, directly or indirectly injuring 
the navigability of said river systems, carried on in said territory other 
than as permitted under the provisions of this Act, is hereby prohibited 
and declared unlawful. 

Sec. 4. That it shall be the duty of said commission to mature 
and adopt such plan or plans, from examinations and surveys already 
made and from such additional examinations and surveys as it may 
deem necessary, as wall improve the navigability of all the rivers com- 
prising said systems, deepen their channels and protect their banks. 
Such plan or plans shall be matured ^\\\\\ a view of making the same 
effective as against the encroachment of and damage from debris result- 
ing from mining operations, natural erosion, or other causes, wdth a 
view of restoring, as near as practicable and the necessities of commerce 
and navigation demand, the navigability of said rivers to the condition 
existing in eighteen hundred and sixty, and permitting mining by tKe 
hydraulic process, as the term is understood in said State, to be carried 
on, provided the same can be accomplished without injury to the navi- 
gability of said rivers or the lands adjacent thereto. 

Sec. 5. That it shall further examine, survey, and determine the 
utility and practicability, for the purposes hereinafter indicated, of 
storage sites in the tributaries of said rivers and in the respective 
branches of said tributaries, or in the plains, basins, sloughs, and tule 
and swamp lands adjacent to or along the course of said rivers, for the 
storage of debris or Avater or as settling reservoirs, with the object of 

( 32;-) ) 



326 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

usinf? the same by either or all of these methods to aid in the improve- 
ment and protection of said navip:able rivers by preventing;: deposits 
therein of debris resultinj; from mininpr operations, natural erosion or 
other causes, or for affording relief thereto in flood-time and providing 
sufficient water to maintain scouring force therein in the summer season ; 
and in connection therewith to investigate such hydraulic and other 
mines as are now or may have been worked by methods intended to 
restrain the debris and material moved in operating such mines by 
impounding dams, settling reservoirs, or otherwise, and in general to 
make such study of and researches in the h^'draulic mining industry 
as science, experience, and engineering skill may suggest as practicable 
and useful in devising a method or methods whereby such mining may 
be carried on as aforesaid. 

Sec. 6. That the said commission shall from time to time note 
the conditions of the navigable channels of said river systems by cross- 
section surveys or otherwise, in order to ascertain the effect therein of 
such hydraulic mining operations as may be permitted by its orders 
and such as is caused by erosion, natural or otherwise. 

Sec. 7. That said commission shall submit to the Chief of Engi- 
neers, for the information of the Secretary of War, on or before the 
fifteenth day of November of each year, a report of its labors and trans- 
actions, with plans for the construction, completion, and preservation 
of the public works outlined in this Act, together with estimates of the 
cost thereof, stating what amounts can be profitably expended thereon 
each year. The Secretary of War shall thereupon submit same to 
Congress on or before the meeting thereof. 

Sec. 8. That for the purposes of this Act "hydraulic mining" 
and "mining by the hydraulic process" are hereby declared to have the 
meaning and application given to said terms in said State. 

Sec. 9. That the individual proprietor or proprietors, or in case 
of a corporation its manager or agent appointed for that purpose, owning 
mining ground in the territory in the State of California mentioned in 
section three hereof, which it is desired to work by the hydraulic process, 
must file with said commission a verified petition, setting forth sucli 
facts as will comply with law and rules prescribed by said commission. 

Sec. 10. That said petition shall be accompanied by an instrument 
duly executed and acknowledged, as required by the law of the said State, 
whereby the owner or owners of such mine or mines surrender to the 
United States the right and privilege to regulate by law, as provided in 
this Act, or any law that may hereafter be enacted, or by such rules and 
regulations as may be prescribed by virtue thereof, the manner and 
method in which the debris resulting from the working of said mine or 
mines shall be restrained, and what amount shall be produced therefrom ; 
it being understood that the surrender aforesaid shall not be construed 
as in any \yay affecting the right of such owner or owners to operate said 
mine or mines by any other process or method now in use in said State; 
provided, that they shall not interfere with the navigability of the afore- 
said rivers. 

Sec. 11. That the owners of several mining claims situated so as 
to require a common dumping ground or dam or other restraining works 
for the debris issuing therefrom in one or more sites, may file a joint 
petition setting forth such facts, in addition to the requirements of 



Appendix] laws affecting placer mining 327 

section nine hereof ; and where the owner of a hydraulic mine or owners 
of several such mines have and use common dumping sites for impound- 
ing dehris or as settling reservoirs, which sites are located below the 
mine of an applicant not entitled to use same, such fact shall also be 
stated in said petition. Thereupon the same proceedings shall be had 
as provided for herein. 

Sec. 12. A notice specifying briefly the contents of said petition, 
and fixing a time previous to which all proofs are to be submitted, shall 
be published by said commission in some newspaper or newpapers of 
general circulation in the communities interested in the matter set forth 
therein. If published in a daily paper, such publication shall continue 
for at least ten days ; if in a weekly paper, in at least three issues of the 
same. Pending publication thereof said commission, or a committee 
thereof, shall examine the mine and premises described in such petition. 
On or before the time so fixed all parties interested, either as petitioners 
or contestants, whether miners or agriculturists, may file affidavits, plans, 
and maps in support of their respective claims. Further hearings, upon 
notice to all parties of record, may be granted by the commission when 
necessary. 

Sec. 13. That in case a majority of the members of said commission 
within thirty days after the time so fixed, concur in a decision in favor 
of the petitioner or petitioners, the said commission shall thereupon 
make an order directing the methods and specifying in detail the manner 
in which operations shall proceed in such mine or mines ; what restrain- 
ing or impounding works, if facilities therefor can be foiind, shall be 
built, and maintained; how and of what material; where. to be located; 
and in general set forth such further requirements and safeguards as 
will protect the public interests and prevent injury to the said navigable 
rivers, and the lands adjacent thereto ; with such further conditions and 
limitations as will observe all the provisions of this Act in relation to 
the working thereof and the payment of taxes on the gross proceeds of 
the same ; provided, that all expense incurred in complying with said 
order shall be borne by the owner or owners of such mine or mines. 

Sec. 14. That such petitioner or petitioners must within a reason- 
able time present plans and specifications of all works required to be 
built in pursuance of said order, for examination, correction, and 
approval by said commission; and thereupon work may immediately, 
commence thereon under the supervision of said commission or repre- 
sentative thereof attached thereto from said Corps of Engineers, who 
shall inspect same from time to time. Upon completion thereof, if found 
in every respect to meet the requirements of the said order and said 
approved plans and specifications, permission shall thereupon be granted 
to the owner or owners of such mine or mines to commence mining opera- 
tions, subject to the conditions of said order and the provisions of this 
Act. 

Sec. 15. That no permission granted to a mine owner or owners 
under this Act shall take effect, so far as regards the working of a mine, 
until all impounding dams or other restraining works, if any are pre- 
scribed by the order granting such permission, have been completed 
and until the impounding dams or other restraining works or settling 
reservoirs provided by said commission have reached such a stage as, in 
the opinion of said commission, it is safe to use the same ; provided, how- 



328 PLACKR MINING FOR GOLD IN CALIFORNIA [BuU. 135 

ever, that if said commission shall be of the opinion that the restraining 
and other works already constructed at the mine or mines shall be suf- 
ficient to protect navigable rivers of said systems and the work of said 
commission, then the owner or owners of such mine or mines may be 
permitted to commence operations. 

Sec. 1G. That in case the joint petition referred to in section eleven 
hereof is granted, the commission shall fix the respective amounts to be 
paid by each owner of such mines toward providing and building neces- 
sary impounding dams or other restraining works. In the event of a 
petition being filed after the entry of such order, or in case the impound- 
ing dam or dams or other restraining works have already been con- 
structed and accepted by said commission, the commission shall fix such 
amount as may be reasonable for the privilege of dumping therein, which 
amount shall be divided between the original owners of such impounding 
dams or other restraining works in proportion to the amount respectively 
paid by each party owning the same. Tlie expense of maintaining and 
protecting such joint dam or works shall be divided among mine owners 
using the same in such proportion as the commission shall determine. In 
all cases where it is practicable, restraining and impounding works are* 
to be provided, constructed, and maintained by mine owners near or 
below the mine or mines before reaching the main tributaries of said 
navigable waters. 

Sec. 17. That at no time shall any more debris be permitted to be 
washed away from any hydraulic mine or mines situated on the tribu- 
taries of said rivers and the respective branches of each, worked under 
the provisions of this Act, than can be impounded within the restraining 
works erected. 

Sec. 18. That the said commission may at any time, when the 
condition of the navigable rivers, or when the capacities of all impound- 
ing and settling facilities erected by mine owners, or such as may be 
provided by Government authority, requires same, modify the order 
granting the privilege to mine by the hydraulic mining process so as to 
reduce amount thereof to meet the capacities of the facilities then in use, 
or if actually required in order to protect the navigable rivers from 
damage, may revoke same until the further notice of the commission. 

Sec. 19. That an intentional violation on the part of a mine owner 
or owners, company, or corporation, or the agents or employees of either, 
of the conditions of the order granted pursuant to section thirteen, or 
such modifications thereof as may have been made by said commission, 
shall work a forfeiture of the jn-ivilegos thereby conferred, and upon 
notice being served by the order of said commission upon said owner or 
owners, company, or corporation, or agent in charge, work shall immedi- 
ately cease. Said commission shall take necessary steps to enforce its 
orders in case of the failure, neglect, or refusal of such owner or owners, 
company, or corporation, or agents thereof, to complj^ therewith, or in 
the event of any person or persons, company, or corporation working 
by said process in said territory contrary to law. 

Sec. 20. That said commission, or a committee therefrom, or officer 
of said corps assigned to duty under its orders, shall, whenever deemed 
necessary, visit said territory and all mines operating under the pro- 
visions of this Act. A report of such examination shall be placed on file. 



Appendix] laws affectixg placer mining 329 

Sec. 21. That the said commission is hereby granted the right to 
use any of tlie pnblic lands of the United States, or any rock, stone, timber, 
trees, brush, or material thereon or therein, for any of the purposes of 
this Act ; that the Secretary of the Interior is hereby authorized and 
requested, after notice has been filed with the Commissioner of the Gen- 
eral Land Office by said commission, setting forth what public lands 
are required by it under the authority' of this section, that such land 
or lands shall be withdrawn from sale and entry under the laws of the 
United States. 

Sec. 22. That any person or persons who willfully or maliciously 
injure, damage, or destroy, or attempt to injure, damage, or destroy, any 
dam or other work erected under the provisions of this Act for restrain- 
ing, impounding, or settling: purposes, or for use in connection therewith, 
shall be guilty of a misdemeanor, and upon conviction thereof shall be 
fined not to exceed the sum of five thousand dollars or be imprisoned 
not to exceed five years, or by both such fine and imprisonment, in the 
discretion of the court. And any person or persons, company, or corpor- 
ation, their agents or employees, who shall mine by the hydraulic process, 
directly or indirectly injuring the navigable waters of the United States, 
in violation of the provisions of this Act, shall be guilty of a misdemeanor, 
and upon conviction thereof shall be punished by a fine not exceeding, 
five thousand dollars, or by imprisonment not exceeding one year, or 
by both such fine and imprisonment in the discretion of the court ; pro- 
vided, that this section shall take effect on the first day of May, eighteen 
hundred and ninety-three. 

Sec. 23. That upon the construction by the said commission of 
dams or other works for the detention of debris from hydraulic mines 
and the issuing of the order provided for by this Act to any individual, 
company, or corporation to work any mine or mines by hydraulic process, 
the individual, company, or corporation operating thereunder working 
any mine or mines by hydraulic process, the debris from which floAvs into 
or is in whole or in part restrained by such dams or other works erected 
by said commission, shall pay a tax of three per centum on the gross 
proceeds of his, their, or its mine so worked, which tax of three per centum 
shall be ascertained and paid in accordance with regulations to be adopted 
by the Secretary of the Treasury, and the Treasurer of the United States 
is hereby authorized to receive the same. All sums of money paid into 
the Treasury under this section shall be set apart and credited to a fund 
to be known as the "Debris Fund," and shall be expended by said com- 
mission under the supervision of the Chief of Engineers and direction 
of the Secretary of "War, in addition to the appropriations made by law, 
in the construction and maintenance of such restraining works and 
settling reservoirs as may be proper and necessary; provided, that said 
commission is hereby authorized to receive and pay into the Treasury 
from the owner or OAAiiers of mines worked by the hydraulic process, to 
whom permission may have been granted so to work under the provisions 
hereof, sucli money advances as may be offered to aid in the construction 
of such impounding dams or other restraining works, or settling reser- 
voirs, or sites therefor, as may be deemed necessary by said commission 
to protect the navigable channels t)f said river systems, on condition that 
all moneys so advanced shall be refunded as the said tax is paid into the 



330 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135 

said Debris Fund ; and provided further, tliat in no event shall the Gov- 
ernment of the United States be held liable to refnnd same except as 
directed by this section. 

Sec. 24. That for the purpose of securinji; harmony of action and 
economy in expenditures in the Avork to be done by the I^iited States and 
the State of California, respectively, the former in its plans for the 
improvement and protection of the navi<;able streams, and to i)revent 
the depositin}; of mininjr debris or other materials \vithin the same, and 
the latter in its plans authorized by law for the ret-lamation, drainaf:?e, 
and protection of its lands, or rclatin*; to the workinj? of hydraulic mines, 
the said commission is empowered to consult thereon with a commission 
of engineers of said State, if authorized by said State for said purpose, 
the result of such conference to be reported to the Chief of Engineers of 
the United States Army, and, if by him approved, shall be followed by 
said commission. 

Sec. 25. That said commission, in order that .such material as is 
now or may hereafter be lodged in the tributaries of the Sacramento and 
San Joaquin river .systems resulting from mining operations, natural 
erosion, or other causes, shall be prevented from injuring the said navig- 
able rivers, or such of the tributaries of either as may be navigable, and 
the land adjacent thereto, is hereby directed and empowered, when appro- 
priations are made therefor by law, or sufficient money is deposited for 
that purpose in said Debris Fund, to build at such points above the head 
of navigation in said rivers and on the main tributaries thereof, or 
branches of such tributaries, or at any place adjacent to the same, whicli, 
in the judgment of said commission, will effect said object (the same 
to be of such material as will insure safety and permanency), such 
restraining or impounding dams, and settling reservoirs, Avith such canals, 
locks, or other works adapted and re(|uired to complete tiie same. The 
recommendations contained in Exei-utive Document numbered two hun- 
dred and sixty-seven, Fifty-first Congress, second session, and Executive 
Document numbered ninety-eight, FortA'-seventh Congress, first session, 
as far as they refer to imi")ounding dams, or other restraining works, 
are hereby adopted, and the same are directed to be made the basis of 
operations. The sum of fifteen thousand dollars is hereby appropriated 
from moneys in the Treasury not otherwise appropriated, to be imme- 
diately available to defray the expenses of said commission. 



Appendix] laws affecting placer mining 331 

AMENDMENTS TO THE CAMINETTI ACT 
Amendment to the 'Caminetti Act,' 1907 

Chap. 2077. An Act To amend section thirteen of an Act of March 
first, eighteen hundred and ninety-three, entitled "An Act to create the 
California Debris Commission and regulate hydraulic mining in the State 
of California." 

Be it enacted hy the Senate and House of Representatives of the 
United States of America in Congress assembled, That section thirteen 
of an Act of March first, eighteen hundred and ninety-three, entitled 
"An Act to create the California Debris Commission and to regulate 
mining in the State of California," is hereby amended so as to read 
as follows : 

"Sec. 13. That in case a majority of the members of said commis- 
sion, within thirty days after the time so fixed, concur in the decision in 
favor of the petitioner or petitioners, the said Commission shall there- 
upon make an order directing the methods and specifying in detail the 
manner in which operations shall proceed in such mine or mines ; what 
restraining or impounding works, if any, if facilities therefor can be 
found, shall be built and maintained ; how and of what material ; where 
to be located ; and in general set forth such further requirements and 
safeguards as will protect the public interests and prevent injury to the 
said navigable rivers and the lands adjacent thereto, with such further 
conditions and limitations as will observe all the provisions of this Act 
in relation to the working thereof and the payment of taxes on the gross 
proceeds of the same : Provided, That all expenses incurred in complying 
with said order shall be borne by the owner or owners of such mine or 
mines: And provided further, That where it shall appear to said Com- 
mission that hydraulic mining may be carried on without injury to the 
navigation of said navigable rivers and the lands adjacent thereto, an 
order may be made authorizing such mining to be carried on without 
requiring the construction of any restraining or impounding works or 
any settling reservoirs: And provided also, That where such an order 
is made a license to mine, no taxes provided for herein on the gross pro- 
ceeds of such mining operations shall be collected. ' ' 

Approved, February 27, 1907. 

Amendment to the 'Caminetti Act,' 1934 

An Act to amend the Act entitled "An Act to create the California 
Debris Commission and regulate hydraulic mining in the State of Cali- 
fornia", approved March 1, 1893, as amended. 

Be it enacted hy the Senate and House of "Representatives of the 
United States of America in Congress assembled, That section 18 of the 
Act entitled "An Act to create the California Debris Commission and 
regulate hydraulic mining in the State of California" approved March 
1, 1893, as amended (U. S. C, title 33, sec. 678), is amended to read as 
follows : 

"Sec. 18. The said commission may, at any time when the condi- 
tion of the navigable rivers or when the capacities of all impounding and 
settling facilities erected by mine owners or such as may be provided by 
Government authority require same, modify the order granting the privi- 
lege to mine by the hydraulic mining process so as to reduce the amount 
thereof to meet the capacities of the facilities then in use ; or, if actually 



;{32 PI-ACKH MINIXC lOU COLD IN CALIFORNIA [Hull. IM.") 

required in order to protect the navijrable rivers from dainafre or in case 
of failure to pay the tax prescribed In- section 23 hereof within thirty 
days after same hccome.s due, may revoke same until the further notice of 
the commission." 

Hec. 2. Section 23 of sudi Act as amended (U. S. C, title 33, see. 
683). is amended to read as follows : 

"Si:('. 23. Upon the coiisti'uctiou by the said commission of dams 
or other works for the detention of debris from liydranlic mines and the 
issuiiifJT of the order provided for by this Act to any individual, company, 
or corporation to work any mine or mines by hydraulic process, the 
individual company, or corporation operatinj? thei'eunder workin<? any 
mine or mines by liydranlic process, the debris from which flows into or 
is in whole or in part restrained by such dams t)r other works erected 
by said commission, sliall pay for each cubic yard mined from the natural 
bank a tax equal to the total cajiital cost of tlie dam, reservoir, and rights 
of way divided by the total capacity of the reservoir for the restraint of 
debris, as (b^termined in each case by the California Debris Commission, 
which lax shall be paid annually on a date fixed by said commission and 
in accordance with refiulations to be adopted by the Secretary of the 
Treasury, and the Treasurer of the United States is hereby authorized 
to receive the same. All sums of money paid into the Treasury under 
this section shall be set apart and credited to a fund to be known as the 
debris fund, and shall be expended by said commission under the super- 
vision of the Chief of Eujiineers and direction of the Secretary of War, 
for repayment of any funds advanced by tlie Federal Government or 
other a<»ency for the construction of restraining works and settling reser- 
voirs, and for maintenance: Proridcd, That said commission is hereby 
authorized to receive and i)ay into the Treasury from the owner or 
dwnei-s of mines wcu'ked by the hydraulic process, to whom permission 
may have been granted .so to woi'k under the provisions thereof, such 
money advances as may be' ofT'>rt>d to aid in the construction of sudi 
im|)oun(ling (buns, oi- other restraining works, or settling reservoirs, or 
sites therefor, as may be deemed necessary l)y .said commission to protect 
the navigable channels of said i-iv(M- systems, on condition that all moneys 
.so advanced shall he refiiiKled ;is the said tax is paid into the said debi'is 
fund: .l//f/ i)nirii!((I fiirllK r. That in no e\eiit shall the (lovernment of 
the United States be liehl liable to reliind sani<' except as directed by this 
section." 

Appr..v.'d..Iuiic l!t. l!i.!4. 

Amendment to the 'Caminetti Act,' 1938 

All iicl III iiiiiciid secfiou 23 of llic Act to cniilc llic ('iilifi)riii(i 
Dihn's (^onmiis^ion, hm (inu nihil. 

Ill it I iiiichil hjf Ihr Siiutfc (Did House of Rrprcsnitativcs of the 
I' nil id Stalls of Ann rini in Cont/rrss assfmlthd, That Section 23 of the 
Act approved March U U^I)3. entitled "An Act to create the California 
Debris Commission and regulate hydraulic mining in the State of Cali- 
fornia", as ameiKb'd by the Act apjiroved June ]!), 1034, is hereby 
further amended by adding at the eiul thereof the following: "The Secre- 
tary of War is authorized to enti-r into contracts to sujiply storage for 
watei- and use of outlet facilities from debris storage reservoirs, for 
domestic and ii-rigation purposes and power (b>velopnient upon such con- 
ditions of delivery, use, and payment as he ma\- a|)prove : Provided, Tiiat 



Al)i)endix] laws Ai'KKcrixd i'i,A(i:ii AriMNd '.]:]'.] 

the moneys I'occivcd from .such (Mmli-ncts shall he deposited to the ci-edit 
of tlie reservoir project t'roiii which the watci' is supplied, and the total 
capital eost of said reservoir, which is to he i-epaid l)y tax ou iiiiuiu^' 
operations as hei-eiu provided, shall he reduced iu the ainount so 
received." 

A|)proved, June 2-"), lt);{S. 



DEFINITION OF HYDRAULIC MINING- 

"Ilydi'aulic iniinui;" is the ])rocess by which a hauk of j^iohUbeariu^' 
earth and rock is excavated l)\' a jet of water, di,schai-^ed through the 
e()nver*i'in<,f nozzle of a pijx' uudei- a ;4reat pressure, the earth or debris 
beinji- carried uwa\- by the .same watei-, thi-ou^b sluices, and disehar<>-ed 
on lower levels into the natural streams and water courses below; wliei'e 
the ^i-avel or other material of tlie baidc is cemented, or wdiere tlie bank 
is composed of masses of pipe-clay, it is .shattered by blastin^' with 
powder. 

DEFINITION OF HYDRAULIC MINING FROM CALIFORNIA CIVIL CODE 
1425. i\reaiHn<ir of hydraulic nunin^^ Hydraulic mininjjj Avithin 
the meaning of this title, is nn'idng by means of the a])plieation of watei', 
under i)ressure, tln-oug'h a nozzle, against a natural bank. 

'■■■ Kicketls, A. }[.. AiiuTiraii .Miniim l-aw; Calif'^ipiu \<\v. .\liiMs ISiiU. 11':;, i). I'.i, 



334 I'LACMK MININt; FOR (lOI.r) IN CATJFOriMA f Rull. 1 3.1 

TRINITY AND KLAMATH RIVER FISH AND GAME DISTRICT 

The following are from the Fish and Game Code : 

97. Trinity and Klamath Kiver district. Tiie following shall con- 
stitnte the Trinity and Klamath River fish and game district : The Kla- 
math River and the waters thereof, following its meanderings from the 
month of the Klamath River in Del Norte County to its contluenee with 
the Salmon River, and also the Trinity River and the waters thereof, 
following its meanderings from its confluence wnth the Klamath River 
in the County of Ilumholdt to its confluence with the south fork of the 
said Trinity River. 

482. (a) It is unlawful to conduct any mining operations in the 
Trinity and Klamath River Fish and Game District between July 1st and 
November .'{Otii, both dates inclusive, except when the debris, substances, 
tailings or other effluent from such operations do not and can not pass 
into the waters in said district. 

(b) It is unlawful between July 1st and November 30th, both dates 
inclusive, to pollute, muddy, contaminate, or roil the waters of the Trinity 
and Klamath River Fish and Game District. It is uidawful between 
said dates to deposit in or cause, suffer, or procure to be deposited in, 
permit to pass into or place where it can pass into said waters, any 
debris, substance or tailings from hydraulic, placer, milling or other 
mining operation affecting the clarity of said waters. The clarity of 
said waters shall be deemed affected when said waters at a point a dis- 
tance of one mile below the confluence of the Klamatli River and tiie 
Salmon River or at a point a distance of one mile below the confluence 
of the South Fork of the Trinity River and the Trinity River contain 
fifty (50) parts per million, by weight, of suspended matter, not includ- 
ing vegetable matter in suspension and suspended matter occurring in 
said stream or streams due to an act of God. 

(e) It is unlawful, between July 1st and November 30th, both dates 
inclusive, to carry on or operate any hydraulic mine of any kind on, 
along, or in any waters flowing into said Trinity and Klamath River 
District; provided, however, nothing herein contained shall prevent the 
operation of a liydraulic mine wliere the tailings, substance, or debris, or 
other effluent therefrom does not or will not pass into said waters of said 
Trinity and Klamath River Fish and Game District, between said dates, 
and provided further that any person, firm or corporation engaged in 
hydraulic mining shall have the right until the fifteenth day of July to 
use water for the purpose of cleaning up. 

(d) Any structure or contrivance wliieh cau.ses or contributes, in 
whole or in part, to the condition, tlie causing of wliich is in this section 
l)rohibited, is a public nuisance, and any person, firm or corporation 
maintaining or permitting the same shall be guilty of maintaining a 
public nuisance, and it shall be the duty of the district attorney of the 
county where the condition occurs or the acts creating the public nuisance 
occur, to bring action to abate such public nuisance. 

(e) Any person, firm, or corporation violating any of the provisions 
of this section is guilty of a misdemeanor. 

(Amended by Ch. 7G0, Stats. 1939.) 



Appendix] laws affecting placer mining 335 

PROTECTION OF DOMESTIC WATER SUPPLIES 

The following is from the appendix of the Fish and Game Code, 33d 
edition, 1943-45, p. 239: 

Section 1. Any person, firm or corporation, other than placer 
mine operators who hold permits from the California Debris Commission 
to operate, who has been engaged or who shall engage in the operation of 
a placer mine on any stream or on the watershed of any stream tributary 
directly or indirectly to the Sacramento or San Joaquin rivers shall 
record in the office of the county recorder of the county in which its mine 
is situate, within 60 days from and after the effective date. of this act, or, 
if operations are commenced after the effective date, then within 30 days 
after the commencement of such operations, a verified statement verified 
by the operator or by some one in behalf of the operator, showing : 

(1) A description of the ground proposed to be mined by placer 
mining methods, described by United States Government subdivisions 
where possible. 

(2) The names and addresses of the owners of the ground. 

(3) The names and addresses of the operators of the mine. 

(4) The proposed means or method of placer mining operation. 

(5) The means which the operator proposes to use to prevent the 
pollution of any stream by the effluent from such operations. 

In the event an owner or operator changes his address, or of a trans- 
fer of ownership or change of operator of any such mining property ,then 
within 10 days after any such transfer or change, a notice setting forth 
the names and addresses of the new owners or operators shall be filed in 
the office of the county recorder. 

Sec. 2. No placer mining operator who does not hold a permit to 
operate from the California Debris Commission shall mine by placer 
process on any stream or on the watershed of any stream tributary 
directly or indirectly to the Sacramento or San Joaquin rivers without 
taking the following precautions to prevent pollution of the stream by 
the effluent from operations : 

( 1 ) Constructing a settling pond or ponds of sufficient size to per- 
mit the clarification of water used in the mining processes before the water 
is discharged into the stream. 

(2) Mixing with the effluent from mining operations aluminum sul- 
phate and lime, or an equivalent clarifying substance which will cause 
the solid material in the effluent to coagulate and thus avoid rendering 
the water in the stream unfit for domestic water supply purposes. 

(3) Notwithstanding the provisions of Subdivision 2 of this section, 
any placer miner who is operating by dredging process and who desires 
to transport his dredger across a stream where the expense of construct- 
ing settling ponds in the stream itself would, in the opinion of the oper- 
ator, be unduly heavy, shall have the right to conduct the dredger across 
the stream without constructing a settling pond under the following 
procedure : The operator shall give to the clerk or secretary, as the case 
may be, of each city or district owning or operating a domestic water 
supply the clarity of which is likely to be affected by the crossing opera- 
tion, notice of the intent of the operator to cross the stream. Such notice 
shall be given at least seven days in advance of the date that the operator 
expects to cross the stream with his dredger. Upon the expiration of 



•'>.■{() I'I.\( i;i{ MIMNd 1(»1< COM) IX ( AMIOHMA [Jillll. 1 :").') 

the IK. lice ll |M'i-;it<.i- iiuiy duiiii:^- I lie lollowiii^' 4S hours coiKhic-t liis 

(Ircdjii'r JiiTi'ss tlic str<'iiiii cvt'u tlioii^li some turbidity nun' be caused 
h\ llif crossiiiii' opfijil ion. llaviipj- crossed the sti'eam the operator shall 
Ihcrcupou aucl thcreat'tei" iu its lurllicr operations ()l)serve the proxisious 
of Subdivision "2 of this section. 

Si;c. :;. Any person, fii-ni or corporation wlio fails to record the 
notice provided for in Section 1. or lo install the protective devices or to 
i^ive the notice provided I'or in Sed ion 2. or both, shall be jruilty of a 
nnsdenieanor. The operation of an.\- pla<M'r mine on <xr<tuml not covered 
by a pei-nnt to the operatoi- from the California ]3e])ris Commission, 
without compliance with the ])i-ovisions of both Sections ] and 2 lier(>of, 
is liere])y declared lo be a public nuisance which may be enjoined upon 
suit brought b.\- the dist rict attorne\ of the county in which the o])eration 
has been conducled. or by an.\- cil\ or district Avliose domestic water 
supply is rendered unlit or daniicrons foi- human consumption by the iu:\s, 
or failure to act, of the operator. The su]ie)"ior court of the county in 
\\ liicli the opci-at ion is conducted shall have jurisdiction to hear and deter- 
mine the action and to awai-d such relief as may be proper therein. 
Xothin;:- in this act contained, however, shall be deemed or construed to 
deprive the State, any city, city and county, county, district, person, firm 
or corporation of any i-ijiht to brinji' and maintain any action or jiroceed- 
in^-. in any jurisdiction, wliicli it was entitled to briuf; or maintain prior 
to the enactment of this act, or to receive or obtain in any such action 
any remedy accoi-ded to it under existin*;' law. 

Si:c. 4. If iiuy section, subsection, sentence, clause or phrase of this 
iu;t is for any reason lield to be unconstitutional, such decision shall }iot 
affect the validity of the remaining;' portions of this act. The Legislature 
hereby declares that it would have passed this act and each section, sub- 
section, .sentence, clause and pln-ase thereof, irrespective of the fact that 
any one or moi'e sections, sul)sectious, sentences, clauses or phrases be 
declared unconstitutional. 

(Added by Ch.rilo, Stats. 1!)41.) 



PLACER MINING DISTRICTS 

Sections 2401 to 2.")12 of the Public Resources Code, i)rovide detailed 
procedure for the formation of placer mininii" districts. To </i\q a j?eneral 
idea of the pur|)ose, the first two .sections are quoted below : 

"2401. Districts iiiiiy lio forinod in tiio nianiuT provided by this chnploi' for the 
imipnse of iiffordiii^' faciiitii's for roiiductiiif; pinci'i- iniiiin}; without iii.juiy to ju-opprty 
iinl Kwiii'd by or inrludcd in the district. 

"'2W2. rn.ccc.lnius (,<y I lie lunii.M i.m of :i pJ.iciT iniiiiiif; district sh:ill he coni- 

I icc<l iiy pctilioii :i(l(ircsscd to iiiid filed with the jjoju'd of siipervi.sors of the poiiiity 

in whi«-h is iocjited the l:M;;est itroportioii in value of the lands within tlie proposed 
district .is shown liy the last e(nialized county assessment roll. The jietition shall he 
signed by twenty-five per cent of the owners of paieels of land sniijcct to assessment 
for distiict purposes." 

As other sections mentioned above are availabh' in the Public 
IJesotirces Co(h> of California i)ublished both by Supervisor of Docu- 
ments, 214 State Capitol, Sacramento 14, aiul by Dancroft-Whitne}' Com- 
l»un\'. 2(1(1 McAllister Street, San I'^raiu-isco 2, they are not repeated liere. 



INDEX 



Aalders, II. J., and Prather, W. W., mining operations in I'lacer County, 271 
Adams mine, I'lacer County, 273 

property, Mariposa County, 261 
Adits, in drift mininpr. SI, S2, S3 
Aerial photo, sliowinp dredged strip of Yul)a Uiver, luO 

photograpliv. ail to eeoloeic study, 153, Ifil, lO.j, 206 
Aetna ohannel, Calaveras County, 237, 23S, 239, 240 
Age of jjlacers, peologic criteria which determine, 1S3-1S6 
Agua Fria Creek, Marii)osa County, 202 
Ahart Ranch. I'lacer County. 276 
Ainlay centrifugal gold savers, 49 
Airola-Costa property, Calaveras County, 2.'j3 
Alanta Mines. Inc.. oi)erations in Placer County, 276 
Alaska, deep secular weathering in, 174 ; beach placers, diagrammatic cross-section of, 

169 
Albiez property. Trinity County, 305 
Albright claim, I'lacer County, 27 4 
Alex Perie proi>erty, San Joaquin County, 282 
Allen, Victor T., quoted, 170 
Allen property, Siskiyou County, 294, 298 

Ranch, Amador County, 231 
Allsman, P. T., cited, 48, 49 

Alpha Stores dredging property, Nevada County, 209 
Amador County, placer mines in, 231-233 

Dredging Company. Amador County, 231 
Amalgam, handling in sampling placer deposits, 222, 223 ; methods of cleaning, 13 4, ]3j ; 
methods of treating, 45, 75, SO, 135, 130 

barrel, in black sand treatment, 79, 133, 134; in Denver trommel-jig unit, 31; in 
dragline dredge cleanups, 45 ; in treating concentrates, 65, 133 

retort, drawing showing, 13S 
Amalgamating plates, use on fine material, 131 
Amalgamation, in jigging, 09; in gold pan, 132; in sluice-boxes, 133; of concentrates, 

131, 132; process explained. 129 
Amalgamator, Berdan pan type, 134 ; clean-up pan type, 133; concrete mixer useil as. 
134 : material requiring use of, 133 ; Titan, 74, 70 ; mechanical type, special 
use of, 133 ; used with jigs, 56 
American Hill, Nevada County, 263 

River, placer mining along, 2S1 : Middle Fork, placer mining on, 255, 250, 271 ; 
South Fork, placer mining on, 255 

Rubber Manufacturing Company, cited, 59, 00 
Amo mine. Butte County, 233 

Ancient channels, 89, i55, 157 ; complexities of geologic history and structure, 161 ; 
methods of tracing, 175 

river terraces, photo showing, 160 
Anderson iiroperty. Placer C<iunty, 272 ; Stanislaus County, 304 
.Angels ((uartz mine, Calaveras County, 237 
Apron, in rockers, 23, 26 
Arbuckle P.rfis., operations in Trinity County, 305 

mine. Trinity County, 305 
Arkansas mine. Nevada County, 269 

Arlington and Osterman properties, Calaveras County, 252 
Arrastre. photo showing use of, 14 

Arroyo Seco Cold Dredging Company. .Amador County, 231 
Arundel Corporation, operations in Yuba County, 315 
Atkins mine, Nevada County, 209 
Auburn Ravine. Placer County, 2 72 
Averill, C. V.. cited. 36, 258, 277, 283, 28.",. 287, 2s9, 294, 300, 303, 305, 307, 309, 310 311 

312, 313 
A>ers, "William, property, Placer County, 272 

B 

B. H. K. Mines, operations in Shasta County, 283 ; operations in Trinity County, 305 

Bacon, E. A., mining operations in Calaveras County, 251 

Badger Hill property. Nevada County, 263 ; photo showing, 207 

Bahr Ranch, Placer County, 272 

Rajada, diagram showing formation in San Joaciuin A'^alley, 198; placers, 152, 161, 160, 

107, 198, 200, 207 
Baker and McCowan. operations in Butte County, 233 ; operations in Plumas Countv, 277 

Ranch, Placer County, 272 
Bald Hill. Calaveras County, 236 

Mountain channel, 291 



338 PLACER MINING FOB OOLD IN CALIFORNIA |BulI. 135 

Ball mill, for treating jig concentrates, 69, 76 ; rib-cone, used in black-sand treatment, 

79, 80 
Barges, pontoon, 39 ; used in dragline operations, 38, 39, 41, 42 
Barker Corporation, operations in El Dorado County, 255 ; operations in Mariposa 

County. 281 ; operations in Tuolumne County. 313 
Barrows, diagrams by, 196 

Batea, description of, 21-22 ; drawing showing, 22 
Batbam, O. K., operations in Trinity County, 305 
Batten properly, Calaveras County, 253 
Bazet Estate property, Trinity County, 305 

Beach placers, diagrammatic cross-section of Alaskan, 169; geologic explanation of, 
1C8-170; Pleistocene and Recent, 205, 207 

sands, photo showing mining of, 78, 168 
Bear Kiver, Placer County, 277 

Beaver Dredging Company, operations in Siskiyou County, 293 
Becker, G. E.. inventcjr of single-bucket dredge, 61 

-Hopkins single-bucket dredge, description of, 61-62; photo showing, 61, 62 
Bedrock, concentration of gold on, 181, 183 ; release of gold from, 163, 174, 175 ; sluice 
grades determined by, 120 

Tunnel placer mine, Nevada County, 263 
Beds, for support of rockers, 23 
Belkriet property, Butte County, 235 
Bellota district, placer mining in, 283 
Belt conveyor, on dragline washing plant, 3 8, 4 3 
Bendelari jigs, on gold dredges, 6G ; tested in New Guinea, 63 
Bent Company, mining operations in Fresno County, 257 
Berg, H. A., mining operations in Madera County, 261 
Berkey, Charles P., cited, 179 

Best, C. L., photo showing gold nuggets from collection of, 290 
Beverly, Burt, photo by, 154 

Bibliography, of California placers and related subjects, 208-216 
Big Blue Lead, at Mayflower mine. Placer County, 274 

Canyon Dredging Company, operations in El Dorado County, 255 

Dipper claim, Placer County, 274 

Ravine, Yuba County, 315 
Biggs Ranch, Sacramento County, 281 
Bilkli property, Butte County, 235 
Birchville, Nevada County, 263 
Birds Eye Canyon mine, Nevada County, 269 
Bishop Company, Thomas B., ownershijj of Vallecito-Western mine, 24 8 

property, Calaveras County, 253 
Black sand, accumulation in riffles, 64; accumulation in rockers, 23; constituents of, 
175; economic possibilities of, 169; nature of California occurrences, 77; 
separation of gold from. 77, 79, 133. 134; separation of platinum from, 
77, 79, 133; small-scale mining of, 79; treatment of, 77-80; treatment in 
amalgam barrels, 133, 134; treatment of amalgam from, 80; valuable 
mineral content of, 77 

-sand load, in jigging operations, 74 
Blackwelder, p:iiot, cited, IGS; diagrams by, 196; quoted, 165, 166, 193, 194, 200 
Bloody Run Creek, Nevada County, 263, 267 
Blowing process in treatment of concentrates, 132 
Blue Canyon, I'lacer County. 273 ; formation. 292 : slate, 292 
Bodinson Manufacturing Company, drawing by. pi. 1 ; photos bv. 30. 38, 40, 46 

sampling machines, 31 ; photo of, 30 

washing plant, 39, 41 
Boe, B., cited, 108 
Boericke, William F., cited, 21 
Booming, in sluice-box operation, 128 

Bottoms, P. H.. mining operations in Merced Countv 262 
Boulders, methods of handling, 41, 61, 85, SS, 113. 114, 128, 222; photo showing forking 

along sluice. 116 ; photo showing handling with derrick. 114 
Bowie. A. J., cited, 98. 118, 120. 121. 123. 128. 130 
Bowling Green property. Calaveras County, 253 
Bradley, Walter W., cited. 145. 260. 263 ; photo by, 164 
Brady, M. A., property in Trinity County, 307 
Bragdon conglomerate, as source of gold. 36 
Bramming, V. E., cited, 71 
Brasswlre Gulch, Siskiyou County, 300 
Breasting, definition of, 81 ; description of methods used in drift mining, 82, 86. 88, 

Brennan. J. P., operations In Shasta County, 283 ; operations in Trinity County. 305 
Brooks, Alfred H., cited, 161 ; quoted. 174. 175, 178 
Brown, M. K., property, Trinity County, 305 

Bros, mine, Nevada Countv, 269 
Browne, Ross E., cited, 271 
Browns Creek, Trinity County, 305 

Hill mine, Nevada County, 269. 270 
Brushy Slide mine. Placer County. 273 
Buck't-elevator use in black-sand treatment. 79 ; use in small-scale placer mining, 34 

- adder dredge, comparison with dragline dredge, 34, 35 ; portable 34 

-line dredge, cost of, .'il; description of bucket, 57. 58; photo showing, 54; photo 
showing latest bucket design. 56 ; photo showing repairing of, 56 

-line dredgmg, description of. 51-60 ; effect on land surface, 52 



;{:}f) 



Bucvrus-lOrie drasline excavator, ."i" 

lUilfards l!ar (lam, Sierra County, 285 

lUilldozer, used witli draRline dredge, lif), 38 , .„ , .1 1^0 

HuUion, gold-, im-tli()<l of molding, HO; sampling methods, 140, 141, 142 

mold, drawing sliowing, 138 
nulolo Cold Dredging Company, jigging tests mad.- l)y, (13 

goldfields, use of I'an-Amerii-an jigs, (iii 
Burns Creek, Mariposa County, 2t;i 

J?urson Mining Company, <,prrat ions in (^alavtias County 2..! 
Uutte County, placer mines in, 233-23r, ; singl.-hm ket dredge operations in, G2 

Operating Company, operations in lUitte County, 233 
nyers property, Calaveras County, 2r)3 
Dyrne claim. Placer Countx, 274-27") 



C. & E. Dredging Company, opeiations in Siskiyou County, 2!)3 ; operations m Stanislaus 

County, 304 
Cady Ranch, San Joa(|uin County, 2.S:', 

Cal Oro Dredging Company, oiieialions in Siskixou County, 293 
Calaveras Cement Company i)roiierty, Calaveras County, 253 

Central mine, Calaveras County, 23r)-247: eliaracter of production, 242-243; costs, 
241-242 ; development, 2:!S-2:i'J ; drag scraping in, 245-240. ; drifting opera- 
tions, Nl ; gravels and channels of, 2:'.C-237 ; history and iiroduction, 230 ; 
mining and milling, 24i»-241 ; project for improvements, 24()-247 ; reserves 
and values of gravel, 2311-240; table of mining and milling costs, 241; 
table showing daily production, 242 ; technology of drift mining in, 243-245 
Central shaft, sequence of strata in, 238 
County, drift mining in, 247-251 ; jilacer mines in, 235-254; Tertiary Central Hill 

channel, i>hoto showing, 151 
Gold Dredging Company, operations in Nevada County, 2G3 
skull, 23G 
California Debris Commission, 203, 270, 273, 325-333 ; see also Caminctti Act 

Gold Dredging Companv, oiierations in San Joatpiin County, 282 ; operations in 

Stanislaus County, 304 
T-iands, Inc., placer mining on laoperty of, 282 
placers, bibliography of, 20S-21(; 
Calkins property, Siskiyou County, 297-298 
Calmo Mining and Milling Companv, Calaveras Cf)untv, 23(;, 239 

shaft, 239 
Camanche district, placer mining in, 253, 282 
Caminetti Act, 2G3, 325-333; affecting debris dams, 144; amendments to, 331-333; 

cited, 159: see also Cdlilornia Drhris Commission 
Canipo Seco district, mining operations in, 253 
Canepa property, Calaveras County, 253 
Canyon Creek, Placer County, 276 

placers. Trinity County, 305 
Capital Dredging Company, operations in Sacramento County, 280 
Carboniferous, Bragdon conglomerate, 3G 

Carmichael Irrigation District, suit against Lost Camp Mining Companv, 273 
Carrville Gold Company, l)ucket-line dredge of, 55 ; operations in Trinity County, 305 ; 

photo showing bucket-line dredge of, 54 
Carson Creek, El Dorado County, 25G 

Dredging Company, operations in Sacramento County, 280-281 
Cassaurang Ranch, Madera County, 2G1 
Cassiterite, tools for, separation of, 21 
Casteca Canyon, Los Angeles County, 2G0 
Cat Camp mine, Calaveras County, 251 
Cateri)illar equipment, 34, 37, 38 

Central Bank of Calaveras, placer mining on projurty of. 282 
distributing system for jigs, G8 
Hill channel, at Calaveras Central mine, 23G, 237, 238, 239, 240; at Vallecito 

Western mine, 248 
placer mine, Nevada County. 2GG-2G7 
Challenge claim. Sierra County, 287 

district, placer mining in, 315 
Champion Flat, Nevada County, 263 

Gulch. Shasta County, 283 
Chaney, Ralph W., quoted, 184, 185 
Chapman, T. G., cited, 131 
Chase Ranch, Mariposa County, 262 
Cheney Creek, Humboldt County, 25 8 
Cherry Creek, Siskiyou County, 293 
Chicken Point mine, Nevada County, 269 
Chico formation, placer reserves in, 152 
Chili Gulch Blue Lead channel, at Deep Lead placer mine, 252 

Deep Blue Lead channel, at What Cheer mine, 254 
China Gulch, Shasta County, 284 

Chittenden. C. N., mining operations in Placer County, 271 
Chocolate Mountains, water courses from, 259 
Christian property. El Dorado County, 257 
Church Union mine, Calaveras County, 252 



:{4() ri.Ac i;k MixiNii lou (;<»i,i) i\ calu'ornma |Ru11. l:i.") 

Cinco Mineros Company, operations in Trinity County, 305 

Cinnabar, tools for separation of, 21 

City-of-Slx channel, 291 

Clark, \V., mininp operations In Calaveras County, 2.)2 

property, Hutte County. 235 

-Jansen pmperty, Trinity County, 309 
Cleaner jip, treatment of concentrates from, 69, 70 

Cleanup-pan, use as amalgamator, 133 . 

Cleanups, in hydraulic mining, 115, 119, 128; in jiRRing, 71, 74; in placer niming. 128, 
129: in platinum-metals separation from gold, 139; in small-scale placer 
mining. 23, 29 
Clear Creek, Shasta Count\ , 283, 284 ; jilacer deposits on, 36 ; Dredging Company, opera- 
tions in Shasta County, 283 
Clerkin property, Nevada County, 263 

Climax Dredging Company, operations in Sacramento County, 281 

Coast Ranges, geology compared with that of Sierra and Klamath regions, 206 ; Ter- 
tiary and Cretaeeous deposition in, 206 
Coffee-Mill channel, at Church Union mine, 252 
Coleburn pro])erty, Nevada C:'ounty, 266 
Collins, F. \V., cited, 71 ; ?,'otrs on jigs for r/old dredges, 73-76 

property. Siskiyou County. 298 
Coloma Creek. El Dorado County, 255 
Columbia Construction Company, operations in Shasta County, 283 

Hill, Nevada County, 265 
Combie Reservoir, Nevada County, 270 
Comet claim. Sierra County, 287 
Concentrates, cleanup in rougher-jig operation, 74 : blowing process in treatment of, 

132 ; rocking in treatment of, 132 ; separation of gold from, 131-135 
Concentrating pans, in Denver mechanical gold pan, 31 
Connelly, R. C, property, Shasta County, 283 
Consolidated placer mine, Nevada County, 266-267 
Contouring of ancient surfaces, usefulness of, 154-155 
Copper plate, amalgamated, use in gold recovery, 23 
Corbett Creek, Mariposa County. 262 
Corley property, Yuba Cf>unty, 315 
Cory and Strong placer, Hutte County, 233 
Cosumnes Gold Dredging Company, operations in Sacramento County, 281 

River, Middle Fork, placer mining on, 2rir) ; North Fork, placer mining on, 256; 
district, jilacer mining in, 2S1 
Cottonwood Creek, Shasta County, 284 
Coyote Creek, Calaveras County, 253 
Craig Osborne property. El Dorado County, 256 

Royce property. El Dorado County, 256 

Salt Water property, El Dorado County, 256 
Cranes, draglines used as, 34, 35 
Cratt property, Butte County, 235 
Cretaceous, Lower, marine sediments of, 170 

conglomerate, as source of gold. 36 

erosion of gold provinces of California, 201 

placers, 170, 186, 206, 208 

sediments, as bedrock for dragline operations, 36 

Sierra Nevada topography, block diagram illustrating, 109 
Crews property. Trinity County, 305 

Crocker-IJuffman I^and and Water Company property, i)lacer mining on, 261, 262 
Crosscut, defined, 85, 86 : breasting in connection with, 87 
Crow Creek, Shasta County, 283 ; Trinity County, 308 

Dredging C<imr>any, operations in Shasta County, 283-2S4 
Crowder and I'.inney proi)erty, Rutte County, 235 
f'rucible, drawing sliowinft, 138 
Cutter and Mueller, operations in Sacramento County, 281 



Dakin Company, mining operations in Nevada County, 263 
Daly Gulch, Shasta County, 284 
Dams, diversion, in hydraulic mining, 99 
Darby property, Rutte County. 235 

and Crowder property. Rutte County. 235 
Dardanelles mine. Placer County, 273 
Daultin. T. M.. cited. 113 
Davidson, George, cited, 171 
Davis, H. W., cited, 139, 140 

Davis, William Morris, cited, 197; diagrams by, 172 
Day, D. T.. cited, 77, 169 
Deadwood district, placer mining in, 293 

Debris dams, coiulitions making constructif>n necessary, 144 ; locations of, 145 
Deep Blue Lead channel, at Hook and Ladder mine. 256 

Lead placer mine, Calaveras County, 252, 254 
Deer Creek, El Dorado County, 255 
Deflectors, table showing weights and prices, 106 
DeKarr and Herbert, operations in Shasta County, 284 



ixDKx ;ui 

Del Norte County beach sands, platinum recovery from, "'^ f.„-mnti..n l.v streinT; 

Delta drawings showing vertical- and cross-sections of, 1S2, foimation, 1)> sticams, 

179, 191 : formation, diagram showing, 19S 
Dennis district, placer mining in, 261 . . , o-. . ,. n,,., ,„.,,.i,inf>« marif- 

Denver Equipment Company, drawing hy, 32; photo by, 3... sampling in<u innos maoe 

mechank-aV gold pan, description of, 31; drawing showing parts of, 32; photo 

showing, 33 
trommel-jig unit, description of, 31-33 
Depleted placers, geologic classification of, l.')l 
Deposition, stream, 1.".3, ir.4, ITS, 17!t, ISI 

Depot Hill hvdraulic mine, Siena County, 2S:, ; photo of. 2S.) 

Derrick, handling boulders with, IH : photo sliowing, 114 . .-o , 

Desert placers, ir.3, l(;i. Did. KiT, liiS. 197. 19>^, 200, 207; reserves m, 1..2; see also 
hujadd placers and dr\i plnrrrs 
processes, in placer formation, 197, U'OO 
streams, erosion by, lit", 2(i0 
Ditert Kstate, Amador County, 2:!1 
1 >iikerson propertv. Trinity County, 301) 
Di<-khaut Ilanch, Calaveras County. 2:.3 

Dip-box, '1\; description of, 27-2S ; iihoto showing use of, 27, 7S 
Disillusionment, in small-scale placer mining, 13. 1."), IS, 19 ... 

Ditclies, 94-9S, 99, 112 ; construction designs recommended. !•<;. 9. ; sluiiing m. li'.i ; spill- 
ways on. 97 ; table sliowing side slopes recommend. d toi-, '.i7 ; table shownifi 
velocities in. 95 
TMtchlines. for hydraulic mining, 99 
]>iversion dams, spillways on, 9I» 
Dobbin Gulch Dredging Company, operaticjns in Shasta County, 2S4 ; operations in 

Trinity County. 307 
Dondero mine. Tuolunuie County, 313, 315 
l-lonnelly, Maurice, cited. 157 

and Johnson property. Nevada County. 2GC 
Doodle bug, dragline dredge, 3 4 
Douglas, Jack, cited, 21 

Jacob property, Butte Ci>unty, L'35 
Dove Mining Company, operations in Yuba C^nmty, 315 
Drag scrapers, used in Calaveras Central mine, 2)5-2_4f; 

Dragline dredges, capital investment re(iuired in T.i3:i, 4n: (.Icunui's, 45: crews. 45, 4*;: 
definition of, :!4: delays in f>perating. 45; disad\ antagcs of. :15 ; <liawiiig 
showing cross-section of riffles. 43 ; drawing showing jilan view (^f. i>I. 1 j 
drawing showing side elevation of. pi. 1 ; moving costs. 45 ; oi)eiating costs 
in 1937. 4f>-4S; photo showing. 3S. 42, 44. If,. 54; iihot.> showing hand- 
wincii. 39 : photo showing iviwer-winch, 40 ; ])lioto sliowing tiomnul. 40 : 
table showing gr)ld ])rodu<tion. 1933-43, 35; used as cranes, :;4. 45; used 
in black-sand treatment, 79 
dredging, descrijition of, 34-4S 
excavators, as digging unit in dragline dredging. 34 ; desciiption of. :'.7 ; nicthoils 

of digging with. 37 ; used with dry-land di-e<lges. 4;t 
machine replacement. 3 4 
Drainage jiattern, drawing showing de\eloi)ment of. 19S 
Dredge construction, future, 00 

hulls, constru<-tion with portable ixmlooiis, 59 
tailing, testing of. f.G. 07 
-tyi)e riffles, drawing showing. 122 
Dredges, drawing showing jig installations on. 70; drv-laiid. (bsniiition of. 411-50: 
factors affecting jig installation on, 07-OS ; op.ialing c.sts for niod.Tu 
typos, 52 
Dredged strip abnig Yuba Uiver. aerial photo showing, 150 
Di-odging, bucket-line, desci-iption of, 51-00; conditions in f'alifornia 0(i • dragliiU' 

description of, :!1-4S; -land, the forming of, 5:; 
Drift, defined, 85, SO 

mining, at Calaveras Central mine, 243-L'45; breasting method.s de.scribed, S7, SS, 
90, 91 ; e<|uipment for, S3, S9 ; explaiuxtion of term, SI ; factors affe<-fing, 
89, *tO; influen<e of ancient channels f>n. S'J ; influence of economic con- 
ditions on, S!t : methods des<ribed, S1-!I2 ; nature of deposits suited to. SI ; 
o|>erating expense, early-day and lec.-nl compared, S!t. 90, 91 : I'lacer 
County, 157; specially designed machines for, ;i] ; .spiling in connection 
with. 85, 80, 87 
l>rifting, breasting in conneetion with. S7 ; cost of. S(;. ST; nietliod and cost of small 

operations. 220 
Drilling, as method of sampling phoer di^posits. 222-220, 227 
Drinkwater, J. C. cited, 144 

Drive-pipe sampling, preparatory to (hedging. 222 
Dry Creek. I'lacer County. 272 ; placer deposits on. 3i; 
-land dredge. oi)erating cost. 4 !t ; photo showing. 50 
-land dredging, description of, 49-50 

placers, 153, 101, 160. 107, 197, 198, 200. 207: effect of wind and sheet floods on 
167, 168: need of geophysical surveying. 157 : see also bnjd'la phncru and 
desert placers 
Duffy property. Kl Dorado County. 255 ; Placer County. 271-272 
Dunn. R. I.... cited. 170 
Durvea mine. Nevada County. 2<)9 
l>utch Flat, riacer County. 271, 272, 270, 277 



342 rr,A(F.R mixin-c; for gold in California [Bull. 135 



East Belt district, placer mining in, 313 

Weaver Creek, Trinity County, 313 
Eastman Gulch, Trinity County, 307 
Eddy, H. P., cited, 96 
Edman, J. A., cited, 169 

Education, facilities available to small-scale placer miners, 18 
Egleston, Thomas, cited, 98 

Eimco-Finlay loaders, used in Calaveras Central mine, 24 4, 245 
El Dorado County, eluvial placers in, 163; placer mines in, 255-257 

Creek, placer mining on, 261 

Dredging Corporation, operations in El Dorado County, 255 
El Oro Dredging Company, operaticjus in Placer County, 272 
Elder property, Nevada County, 2 OS 

Electric power, large expense in bucket-line dredging, 52 
Elephant hydraulic mine, Amador County, 231 
Elevator, hydraulic, 106, 107, 108; drawing showing. 111 

Ruble, drawing showing, 108 ; for use in hydraulicking, 106 ; i)hoto sliowing, 110 

step-lift, used in hydraulicking, 107 
Eliel, Leon T., cited, 153 
Ellsworth, E. W., cited, 227 
Eluvial placers, geologic explanation of, 103 
Emigrant mine, Nevada County, 20 ft 
Emma mine, Butte County, 233 

Gordon property. El Dorado County, 257 
Engineering and Mining Journal, photos supplied by, 150, 160, 204 ; reprint from, 317-322 
English, Walter A., cited, 153 
Eocene beach-placers, 170 

channels, 263, 266, 276, 287 ; gold values in, 170, 175, 208 

structural control of gold provinces, 201 
Eolian placers, geologic explanation of, 167, 168 

Erosion, Cretaceous, of gold provinces of California, 201 ; cycle of, 194 ; effect on gold 
concentration, 181; of bajada placers, 160; of lakes in Sierra Nevada, 
205; of residual placer, 163: of streams, 165, 171, 178, 186, 187. ISS, ISU, 
194, 197 ; on river bend, diagram showing, 177 
Esco bucket, for dragline dredging, 37 
Esperance mine. Nevada County, 263, 264, 205 

Etna Gold Dredging Company, operations in Siskiyou County, 293 
Excavators, draglines used as, 34 

dragline, discription of, 37 
Excelsior mine. Placer County, 273, 274 
Exploration methods, significance of improved, 152-154 
Explorers, Inc., property. El Dorado County, 255 ; Mariposa County, 261 



Fair Oaks, Sacramento County, 282 ; Gravel Company, operations in Sacramento 

County, 282 
Fairbanks, H. W., cited, 157 

Fairchild Aerial Surveys, Inc., map furnished by, 202 
Fancelli property. Trinity County, 309 
Farnsworth mine. Siskiyou County, 293 
Fassett-Parker-Hanlon property, Sacramento County, 2S1 
Fault blocks, drawing showing down-dropped and uplifted. 172 

zones, map showing major California. 158 
Faults, gold deposits in, 173, 204, 205, 207 
Feather River, placer reserves, 152 
Ferrari property. Placer County. 276 
Ferreva Ranch, Placer County, 276 
Filibuster Flat, Trinity County, 313 
Finch, R. H., cited, 193 

First Chance property, Yuba County, 315 
Fish and Game Code, extracts from, 33 4, 335 

Ranch, Shasta County, 284 
Fisher and Baumhoff, cited, 63, 71 

property. Calaveras County, 253 

r^anch, Placer Countv, 275 
Flat Creek. Shasta County. 284 
Flint, R. F.. quoted, 187, 191, 193 
Flotation, for fine-gold recovery, 65 
Flow-sheet for use of jigs, 75 

Flumes, cost and method of constructing wooden, 99 ; photo showing construction of, 92 ; 
.safety measures In connection with. 99 ; use in hydraulic mining, 98 ; use 
with long toins. 28 ; working auriferous gravels in, 29 
Folsom district, placer mining in, 278, 281 
Forest, Sierra County, 291 

Hill Divide, drift mines of the, 271 

Service, regulations for placering, 20-21 
Forestblll. Placer County. 271. 273. 276 
Forschler Ranch, Shasta County, 284 



INDEX 348 

Forsyth and Lewis property, Placer County, 275-276 

Fossils, significance of, 184, 188 

Foster Ranch, San Joaquin County, 282 

Francis formula, for calculating water flow, 98 

Franke. H., cited. 235 

Fraser and Alexander property, Nevada County, 263 

Freidel property, Butte County, 235 

French Corral placer mine, Nevada County, 263-265 

(.Julch, Shasta County, 284 ; district, source of Clear Creek placers, 36 ; Dredging 
Company, operations in Shasta County, 284 
Fresno County, placer mines in, 257-258 

River, placer mining on, 261 
Fretz, property, Mariposa County, 262 
Friant dam, Fresno County, 257 
Froloff property. Trinity County, 309 
Fulda Creek, I'lacer County, 273 



t;-B portable placer machine, description of, 33 
<Jail placer mine, Nevada County, 209 
Gallia mine, Siskiyou County, 293-294 

Placer Mining Company, The, operations in Siskiyou County, 293-294 
(Jamble, V., property, Butte County, 235 
Gardner, E. D., cited, 48. 49, 81, 83, 93, 131, 175, 219, 221, 225, 226, 268, 285, 293, 

294, 298, 310, 311 
Garibaldi mine, Amador County, 231 
Garland Mill Slope mine. Placer County, 273, 27 4 
Gas Point, geology in vicinity of, 36 
Gaskill property, Mariposa County, 262 
(Jasper property. Trinity County, 313 
Gaylord, H. M., cited, 229, 258 : quoted, 35 

Gem stones, jigs used in recovery of, 63 ; tools for separation of, 21 
General Dredge property, Siskiyou County, 298 

Dredging Corporation, operations in EI Dorado County, 255 ; operations in Sacra- 
mento County, 281 
(lenetic types of placers, 161 
(Jenochio pro)>erty, Calaveras County, 252 
Cicologic age of placers, 183-186 
classifications of placers, 150 

conditions in gold provinces of California, 200-201, 204-206 
map showing prevolcanic topography, 156 
Geology of placer deposits, 150-216 : bibliography, 208-210 
Geomorphology. 153 : see also physiograpliy 
Geophysical prospecting methods, 227 

surveying, 153, 161 ; as aid to geologic study, 206 
Germain, A. G., operations in Stanislaus County, 304 

Giants, number and size in use in 1932, 113 ; photo showing, 104 ; photo showing stack- 
ing of tailings with, 117 ; table showing flow of water through, 107 : table 
showing sizes, weights, and prices, 106; use in hydraulicking, 94, 99, 
105-100, 112, 113 
Gibson, M. K., Mining Company, operations in Nevada County, 265 
flilbert, F. C, quoted, 188, 189 

G. K., cited, 119, 187; diagrams by, ISO, 1S2 ; quoted, 189, 190, 191 
Gill, Corrington, cited, 13 
(Jivens property, Mariposa County, 261 
(Jlacial placer deposits, 161, 165. 166. 193, 194 
Gladding Ranch, Placer County, 271 
Glo-Bar Mines, operations in Calaveras County, 252 

flold, accumulation in rockers, 23, 26; amalgamation with quicksilver, 31, 42, 135, 136; 
amalgamation in sluice-boxes, 133; balances for weighing, 141, 142; 
extraction from amalgam, 135-137 ; in beach sands, economic importance 
of, 169 ; in dredging areas, nature of, 53 ; in placer samplings, method of 
calculating, 223; in placers, geologic explanation of origin of, 173-174; 
marketing of, 142-143; melting process for marketing, 140; method of 
shipping, 142, 143 ; release from bedrock, 174, 175 ; separation of platinum- 
group metals from. 137-140; separation from black sand, 77. 79, 133; 
separation from concentrates, 131-135 ; table showing California produc- 
tion, 1848-1944, 16-17; table showing production from dragline dredging, 
1933-43, 35 ; transportation, deposition, retention in str ms, 178-181 
Acres mine, Shasta County, 285 
Bluff district, placer mining in, 258 
bullion, molding process, 140 
Delta placer mines. Imperial County, 259 

dredging, flrst attempts in California, 51 ; jigging applied to, 63-76 ; principle of, 53 
Hill Dredging Company, operations in Butte County, 233 ; operations in Calaveras 

County, 252 : operations in San Joaquin County, 282 
nuggets, formation of, 179 
pan, description of, 21-22, 133; drawing showing, 32; mechanical, 31-33; use of 

amalgamation, 132 ; use in sampling natural exposures, 220 
Placers, Inc., operations in Placer County, 272 
price increase, effect on small-scale placer mining, 14 



344 IM.AI KK AIIMNC lOK COM) IN ( AI.IFOKNIA |liull. IM.") 

Gold — Continued „„ ^ „„„ 

provinces, geologic conditions in California, 200-201, 204-206 

-quartz veins, erosion of, 36 

Recoveries Corporation, operations in Placer County, 272 

recovery, photo showing primitive methods, 14 ; undercurrent method or, 127, 128 

Reserve" Act of 1934, cited, 140 

Run, riacer County, 271. 276 

-saving, by riffles, theorv of, 121 ; table arrangement, 57 

Valley Dredging Company, operations in San Joaquin County, 282 
Golden Belt Mining Company, cost of running drift for, 86, 87 

Feather Dredging Company, operations in Butte County, 233-234 

Gravels Mining Comi)any, operations in Trinity County, 307 

River Mining C(imi)any, operations in Calaveras County, 252 
Goldtleld Consolidati-d Mines Company, operations in Trinity County, 307, 311; photo 

showing hydraulic mine, 306 
Good Luck mine. El Dortulo County, 255 
Gould, James L., property in Placer County, 277 
Grant Pacific Rock Company property, Fresno County, 258 

-Service Rock Company, operations in Fresno County, 257 
Gray Lead channel, at Hook and Ladder mine. 255-256 
Great Basin region, bajarta placers in, 167, 207 ; Pleistocene faults in, 171, 173, 204, 207 

Valley, placer deposits in, 205, 206 
Green Spring mine, I'lacer County, 273 
Greenhorn Creek. Nevada County, 269 

district, placer mining in, 293, 298 

Dredging Company, operations in Kl Dorado County, 255 

mine, Nevada County, 269 
Greenwood Creek, El Dorado County, 255 
(Gregory Ranch, Calaveras County, 253-254 
Griffith Company, mining operations in Fresno County, 257 

Grizzly, as feeder to undercurrent, 30 ; as part of Ruble elevator, 106 ; function in drag- 
line dredging, 41 ; function in hydraulic mining, 115, 127 ; function in 
sluicing, 2!" 

Canyon, Nevada County, 267 
Gruwell, C. E., mining operations in Calaveras County, 252 ; operations in San Joaquin 

County, 283 : operations in Shasta County, 284 
Guttinger, Albert, properly, Calaveras County, 253 

John, property, Calaveras County, 253 



Ilageman property, Calaveras County, 253 

-Huberty i)roperty, Calaveras County, 253 
Haley, C. S., cited, 144. 159 

Hall and French, operations in Nevada County, 265 
llallstrom and Lindblad, mining operations in Placer County, 2 72 
Ilalt.r mine, Calaveras County, 254 

Jlammon Engineering Company, work at Hook and Ladder mine. 256 
Hammond, John Hays, cited, 242, 273 
Hand methods, in small-scale placer mining, 19 

-winch, for dragline dredge, photo showing, 39 
Happy Camp Dredging Company, operations in Siskivou County, 294 

Valley, Shasta County. 2S4 : Blue Lead, operations at, 254 ; Land and Water Com- 
pany. i)lacer mining on property of. 285 
Ha(|uinius, E., cited. 153 

Harms Bros, and Larsen Bros., o))erations in Siskiyou County, 294-297 
Harrin, Mary, property. Butte County. 235 
Harz jig. use in early jigging i)ractices. 66 
Havilah Gravels. Inc., operations in Trinity County. 307 
Hawkins Canvon, Neveda C<junty, 269 
Hay, Oliver P., cited, 185 
Hayfork, Trinity County, 305 

district, placer mining in, 312 ' 

Hazelroth claim. Placer County. 274 
H.izen. Allen, cited, 93 

Helen Whittier property. Butte County, 235 
Henry. J. H., mining operations in Calaveras County, 252 
Henshaw, Paul C, cited. 259 

Hiatt, Wm. P., Ranch, mining operations at, 253 
Hidden Channel, Trinity County. 313 
Higglnbotham property, Stanislaus County. 304 
High Channel mine. Trinity County, 312 
Hill. J. M., cited, SI ; quoted, l.;7 
Hinds, Norman E. A., cited, 36, 157 
Hodgkin, Emma J., prfipcrty. El Dorado County, 256 
Hoefling Bros., operations in San Bernardino County, 282 
Hogate R.anch, Calaveras County, 252 
Holcomb Valley district, placer mining In, 282 

Valley P','^^^,,'^.""^'j,'i,'">'' "Perations in Kern County, 260; operations in Sacramento 

Hook and Ladder niine. El Dorado County, 255-256 ; Trinity County, 305 
Hoosier Gulch Placers, operations in Sacramento County 281 
Hoover, H. C, cited, 161 



i\i)i;x .'Uf) 

lldpc inillf, I'hKci- Ciiunly. liTo 

llDpkitis 11 11 iiiMiilur nf sitmlt'-bucket dreclRe, Gl 

iin<l'l^'<K.r. iiiitiitiK •■!'»iati<.ii.s ill Kn-sii() Ooinity, ^.-,7 , ,■. ,oo.,. 

llnppiT ill Dmv.r in.M'lianic;,! j;..l.i p:tn, :! 1 ; in ,lip-li..x, ■^S ; in diaKlinr iln-.lgmn, ns, 41 ; 

in C-i: portal. Ir pla.-.r inadiinc, :!:! 
lloniiaii claim, I'la-cr Cniinly. JTI. JT:. 
llnnu.r. U. K.. cil.d, Ki'.' 
Uursf Cri'oU, iilacrr niiiiin;; mi, I'lil-l'l'. 
lli.r.M-hi.f Bar, 101 Durad'i ('"unty, :;:.ii ; I 'hi<« r < 'miiity, J i L • ■ ,. i 

Dri-tlniiiK Company, oimrat ions in Ama.loi' ('Munly, J.; I ; op.iat s in ( alavfras 

Connly, :;r.2 ; operations in lOl l>oi;olo < oiiiit.\, ...h 
llorton. V. "SV., cited, 235, 24,S, 2GI 

K. E., cited, HG 

mine, Amador County, 231 

Culch mine, Siskiyou County, 294 
llotchkiss Suiierdip maKnetonieter, 227 

Huelsdonk, ].. I.., A syiioiitic prcsunipt ion rtiionluuj Calil oniia'.s dnjt iiiiiks. s|i-;i1 ; 
photos by, 2S.S, 2Sit, 29" 

concentrator, use in Calaveras Centra! mine, 211 
Hughes property, VA Dorado County, 25.') 
Huliii, C. 1)., citid, 157, 107 
Hulls, for bai-Kcs, constructif>n, 39; for Inicketline dredf^es, iiortab!.' pontoon construe- 

tion, 59 
Ilumbfddt County, placer mines in, 25.S-25!t ; workin.t; of beaili sands, 7S, 79 
IJumbuK' Cre.-k, Nevada County, 2ii7 ; Siskiyou County, .'.nu 
Hume and Coleman iirojierty, liutte County, 235 
Humiihrey.s Cold Coriioralioii, dry-land dredKcs built by, 19; ojieialioiis in liulte 

County, 234 ; operations in Sacramento Counl\, I'M 
Hungarian riffles, in bucket-line dredging, 5.;; in dragline dre(lK<- cleaning, 45; use in 

Calaveras Central mine, 241 
Hunt Ranch, Calaveras County, 253 
Hunter Valley district, placer mining in, 2G1, 2G2 
Hutchison i)roperty, Sacramento Count.v. 2S1 
Hydraulic classifier, used for sizing black sands, 77 

ditches, table showing velocities in, 95 

elevator, lOi;, 107, lUS; drawing showing, 111 

jig, 73, 74, 79 ; see also pulsator jig 

mine, photo of flume for, 92 ; photo showing pipe installation, lUU 

mining, application to placer methods, 9.",-ll(;; costs, :):; ; damage from, 144 ; detini- 
fion of, 333; early-day practices, H>S : eMUiiiment, 99; t.ipe-liiies for, 
100-105 ; sampling in connection with, 22ii ; water supply lor, 93. 94 

I 

Igo, gravel deposits in vicinity of, :'.G 

district, i)Iacer mining in, 283, 2,S4 
Imperial County, placer mines in, 259-200 
Independence fault, 202 

gold mines, Amador County, 231 
Indian Canyon, Placer County, 272 

Creek, Kl Horado County, 25t; ; Siskivr.u Countv, 293 

Hill mine. Sierra County, 2S5, 287 

Springs mine, Hutte County, 233 
Ingram, W. I)., mining o]ierations in Kl Dorado Countv, 25C ; mining oiierations in 

Placer County, 272 
Innis, A. B., operations in Nevada County, 205 

]>redging Company, operations in Placer Countj-, 272; operations in Plumas 
County, 277 
Interstate Mines, Inc., operations in Butte County, 234 ; oiierations in Trinitv County, 307 
lone formation, 152, 170, 1S4, 20S ; defined, 170 
Iowa Hill district, placer mining in, 272, 274 
Irish claim. Placer County, 274, 275 

Creek Mining Comjiaiiy, ojjerations in Kl Doratlo County, 250 

Hill mine, Amailor County, 232 
Irvine, K. S. J., cited, 144 



.lackass property, Tuolumne County, 313 

Jackson, T. H., cited, 144 

Jamieson, T. G., drawing supplied by, 155 

Jamison Creek, Plumas County, 277 

Janin, Charles, cited, 130 

Jarman, Arthur, cited, 144, 2G3, 2G8, 209 

Jasper-Stacy Company, operations in Placer County, 272 

Jenkins, Olaf P., Neic technique applicable to the study of placers, 150-208 ; Physio- 
graphic map of California, 158 ; cited, 185 ; quoted, 181, 183 

Jenny Kind district, placer mining in, 253, 282, 283, 300, 304 
Lucas property, San Joaquin Count>\ 282 

Jig, as bucket-line dredge equipment, 53, 55 ; as gold dredging equipment, 03-70 ; 
central distributing system for, C8 ; in Denver trommel-jig unit, 31 ; tailing 
recovery by means of, 07 ; testing before installation, 07, 73 ; use of, 
compared with riffles, 03, 04 
arrangements, drawing showing, 70 



'14r. PLACKR MINIXfi FOR OOLD IN CAI.IFORN'IA [BuH. l-'M 

Jig — Cotitlnuod 

Hendelari. use on buckct-lii.e dredges, SS 

cleaner-, treatment of concentrates from, 60, 7fi 

Harz, used In early jlRRing, r>6 

Installation, factors affectinp, f.7, 68 

Pan-American Pulsator, 73. 74, 79 

placer, 5 .1. 63. 66 

recovery factors affectinpr. 67, 68 

rougher, 68, 69, 73, 74 : photo shf>wing 4-cell block, 74 

scavenger, 68, 60, 73, 74 

testing set, photo showing, 72 

Yuba, fidaptations of, 55 
Jigs, cleanuiis from, 71 : comparative use as essential and auxiliary equipment In 
dredging, 69, 71; development of operating methods since 1037, 73-76; 
factors affecting installation, 67, 68 ; factors affecting operation of, 67, 68 ; 
fU)W sheet for use of, 75 
John Aim property, Rutte County, 235 

Hilkli tiroperty, Hutte County, 235 
Johnson, C. H., cited, 81, 93, 131, 175, 219, 225, 226, 268, 285, 203, 294, 298, 310, 311; 
diagrams by, 169, 192 

Douglas cited, 194 

K. W., Ranch, Calaveras County, 236 

J. F., cited, 83 

Itanch, TMacer County, 271 

Walter W. Company, details of dredge construction furnished by, 300 
Johnsville district, placer mining in, 277 
.lones, J. Wesley, quoted, 52 
Joshua Hendy Iron Works, cited, 105; table on flow of water through giants supplied 

by, 107 
Joubert mine, Siskiyou County, 29 4 
Julilin, C. K., cited, 235, 248, 261 
Junction City Mining Company, operations in Trinity County, 307-308; photo of 

dredge, 306 
Jupiter mines, Nevada County, 269 ; mine, Placer County, 274 



Kaasa property, Stanislaus County, 304 
Kalbaugh, C. L., operations in Trinity County, 308 
Kaneko Ranch, Placer County, 276 
Kaiilan mine, Tuolumne County, 313, 315 
Kate Hayes property. Nevada County, 263, 265 
Kates mine, El Dorado County, 257 
Katesville Culch, Sacramento County, 281 

Kaulfield and Danison, operations in Butte County, 234 ; operations in Nevada County, 
265 

and McKinley, operations in Nevada County, 265 ; operations in Placer County, 272 
Kehoe property. Mariposa County, 261 
Kenna mine. El Dorado County, 257 
Kent, E. A., operations in Tuolumne County. 313 

property. Amador County. 232 
Kentucky Flat. F:1 Dorado County, 257 ; mine, 257 

placer, workings at, 252 
Kern County, placer mines in, 260 
Kerr, W. C, cited, 175 

Keystone drill, designs and distributors, 222, 223 
Kiessling. R. T^., cited, 13 
King Solomon mine, photo showing. 164 
Kipi). P'rank. property. 101 Dorado County. 256 

Klamath Mountains, geology of placer deposits in. 152, 157. 159. 163. 173. 207; gold 
provinces in. 200-201. 204-206 

River, placer mining on. 258, 294, 297, 300; district, placer mining in. 298. 300 
Knights Ferry district, placer inining in. 304 
Knopf. A., quoted. 187. 191, 193 
Kr>ehrlng dragline excavator, 37 
Kohle, Fred, property, Shasta County. 284 
Kutter formula, for determining velocity in ditches, 95, 98 

modification of Chezy formula, 103-105 



I>a Bienvenlta mine, Tuolumne County, 313 
fJrange district, placer mining in, 304 

fJold Dredging Company, operations in Merced County, 262 ; operations in 

Stanislaus County, 304 
Placer Mines, I^td., operations in Trinity County, 308 
property, 313 
Kamp Pros., operations in Placer County, 272 
I'orte channel, 2 87 
dl.strlct, 277 
T^aizure, C. McK., cited. 31. 79. 261 
I..ake Spaulding. Nevada County. 266 

Lakes, formation by landslide, sketch showing. 172; geologic relation to stream Chan- 
nels, 197, 200, 201, 205 



INDEX 347 

T.anchii Plana. Amador County, photo showing removal of overburden at. 286 d„.,„ 

J.ancn.i ^^J'^^-^^'^^j company, operations in Amador County 232 ; operations »n Butte 

(Guilty. 2.34 ; operations in Calaveras County. 253 ; operations In Sacra- 
mento County, 281 w , no 
Landslide, sketch showing lake formation as result of, 17<J 
Lange property, Siskiyou County, 293 „. , . ^ . on, om 
Larsen Bros. km\ Harms Bros., operations In Siskiyou County, 294-297 
Lava flow, Tuolumne County, photo showing, lo4 
Laws, affecting placer mining. 323-336 : regulating ore buyers, 143 
Leahy vibrating screen, use in Calaveras Central mme, 241 
Leak Ranch, I'lacer County, 272 
Leal property, Butte County, 235 

Lebanon Consolidated Mines, operations m Placer County, -i^ 
Lee, C. I-'., cited. 113 _ 
Lemroh Mining Company, operations in Butte County. 234; operations in VA Dorado 

County, 256 
Lewallen Ranch, San Joaquin County. 283 
Lewiston district, placer mining in, 309 

Placers, operations in Trinity County. 308 
Liberty district, placer mining in. 293, 29 4, 298 
Lightner mine, Calaveras County, 237 
I^ights Canyon district, placer mining in, 277 

Creek, Plumas County, 277 
Lima dragline exea\ator, 37 

Lincoln district, placer mining in, 271, 276 • ou * 

Gold Dredging Company, dragline dredge, photo of, 309 ; operations in bhasta 

Countv, 284 ; operations in Siskiyou County, 297-298 ; operations in 

Trinity County, 309-310 
Linden district, placer mining in, 283 „ . „„„ 

Lindgren, Waldemar, cited, 144, 152, 154, 157, 173, 179, 181. 233, 2oo, 269; drawings 

by, 162, 177; quoted, 163, 170, 173, 174, 179, 184 
Link belt dragline excavator, 37 

Lithologic criteria, determination of age of placers by, 185, 180 
Litsch, Robert, propertv, Shasta County, 283 
Little Browns Creek, Trinity County, 305 
Uttlejohn Creek, placer mining on, 304, 305 
Live Oak mine. Placer County, 273 
Living conditions, for small-scale placer miners, 18-20 
Lobicasa Company, operations in Butte County, 234 ; operations in Calaveras County, 

253 
Lobicassa Company, operations in Plumas County, 277 ; operations in Sacramento 

County, 281 ; operations in San Joaquin County, 282 
Lode production, table showing ratio to placer production, 1848-1930, 158 
Loftus Blue Lead Mining Company, operations in Sierra County, 287 
Logan, C. A., cited, 36, 163, 233, 235, 255, 263, 271, 274, 277 
Log-sheet in sample drilling, 225 
Logtown property, Sacramento County, 281 
Lombardi property, Calaveras County, 253 

Long Bar Gold Dredging Company, operations in Amador County, 232 
Point Mining Company, operations in Placer County, 274 
tom, description of, 28-29 ; drawing showing, 28; in dragline dredge cleanups, 45; 

separation of platinum metals, 139 ; treatment of beach sands, 79 
Longwell, C. R., quoted, 187, 188, 191, 193 
Lord, J., property, Mariposa County, 261 

and Bishop, operations in Butte County, 234; operations in Calaveras County, 253 
Lorentz property, Amador County, 232 
Lorrie property, Butte County, 235 
Los Angeles County, piacer mines in, 260-261 
Lost Camp mine, Placer County. 273 
Louis. Henry, cited, 137 
Love Ranch, Placer County, 272 
Lowden Ranch, Trinity County, 307 

Lucky Charles ^Mining and Milling Company, cost of running drift for, 87 
Lyons Ranch, Tuolumne County, 313 

M 

MacBoyle, Errol, cited. 263, 277 

MacDonald. D. F., cited, 124 

Macaulay, W. B.. cited, 260 

Machado property, Mariposa County, 262 

Madera Countv, placer mines in, 261 

Magee, J. F., cited, 36 

Magnetic separator, for sizing black sands, 77 

Mahon property, Sacramento County, 281 

Malakoff hydraulic mine, Nevada County, 268, 267 

Malozemoff, P., Jigging applied to gold dredging, 63-72 

Mammoth Mining Company, operations on property of, 315 

Marine fauna, use in determining geologic age, 184 

placers, 161, 168-170, 205, 207, 208, see also beach placers; possible areas con- 
taining, 150 

sediments, Lower Cretaceous, 170 
Marion dragline excavator, 37 



:US i'(,A( i:k mining; for fjoi.D i\ califoknia |RuI1. liio 

Mariposa County, placer Initle^i in, 261-2G2 

Markets, for placer gold, 142-143 

Marsh, K. A., property, Calaveras County, 252 

Marshall. James, discovery of gold by, 255, 260 

Martel property, Xe\ada County, 265 

Martell Kavine, Kl Dorado County, 25C 

Mats, used in moving dragline excavators, 37 

Matlhes, Krangois E., diagram by, 190; quoted, 185 

Mattison shaft, Calaveras County, 230 

Matulich property, Amador County, 232 

Max and Junction mine, Kl Dorado County, 256 

Mavflower Cravel Mining Companv, operations in Placer County, 273-274 

McAdams Creek, Siskiyou County, 293 

McConnelJ Bar, Siskiyou County, 300 

M(('ulloh property, Amador County, 232 

MiKlroy mine, Calaveras County, 236 

shaft, Calaveras County, 236, 237, 238 

McCain. Roy, photo by, 259 

Mcdeachin I'lacer Cold Mining Company, operations in Placer County, 273, 274-275; 
photo showing sampling of hydraulic bank, 275 

McCee, W. J., cited, ISO 

McCuire, A. It., partner in single-bucket dredge operation, 62 

McCurk property, San Joaquin County, 283 

McKinely, H. W., mining operations in Placer County, 275 

McMillan and Company, operations in Tuolumne County, 313 

MiQueen and Downing, operations in Amador County, 232 ; operations in El Dorado 
County, 256 ; f)i)erations in Sacramento County, 281 ; operations in Siski- 
you County, 298 

Meadow Valley, Plumas County, 277 

Measuring weirs, use in hydraulic mining, 98 

Mechanical jig, 55, 63, 66 

Mehrten Bros., operations in Calaveras County, 253 

Melting furnace, in black-sand treatment, 79 
Menke-Hess property, Tuolumne County, 313 

Merced County, placer mines in, 262 

Dredging Company, ojierations in Merced County, 262 
River, placer mining on, 262 
Merrill. C. \V., cited, 13, 45, 229, 258 ; quoted, 35 
Frederick J. H., cited, 157 
v.. P., cited, 174 
Mertie, J. B., Jr., cited, 161 ; quoted, 165 
Metcalf, L., cited, 96 
Michigan Bluff, Placer County, 271 

Midas Placer Company, operations in Calaveras County, 253 
Midland Company, Inc., operations in Placer County, 275 ; operations in Siskiyou 

County, 298 
Milner. H. B., cited, 175 

Milton placer mine, Nevada County, 203, 205 

Mine and Smelter Supply Company, sampling machine made by, 33 
Miners Ravine, Placer County, 272 
Mining methods, placer, 11-146 
Mississippi mine. El Dorado County, 257 
Missouri Canyon mine, Nevada County, 269 
Moccasin mine, Siskiyou County, 297 ; cost of equipment set up at, 297 ; dragline dredge 

in use at, 34, 35 ; photo of dragline dredge at, 296 
Mofflt, Fred H., cited, 168 
Mojave desert, bajada placers in, 167, 207 ; geology of stream placers in, 157, 163, 171, 

173, 207; Pleistocene faults in, 173, 204, 207 
Mokelumne Tracers, Ltd.. operations in Calaveras County, 254 
River, mining operations along, 252, 253 

Sand and Gravel Company, operations in San Joaquin County, 282 
Monarch Rand mine, Kern County, 260 
Monighan dragline excavator, 34 

Monit<jr, see f/iant • 

Montgomery property, Shasta County, 284 
Monumental Creek, Placer County, 273 
Mooney, Jose|)h, Ranch, F'lacer Countv, 272 
Morgan property, El Dorado County, 256 
Mormon Bar, placer mining at, 262 
Morning Star drift mine, Placer County, 274 

Morris Ravine Mining Ccjmpany, operations in Butte County, 234 

Mother Lode, aerial map showing, 202 ; relation to Calaveras Central mine, 237 ; dis- 
trict. i)la<er mining in, 261 
Mound City Cold Mines, Inc., property in Calaveras County, 239 
Mountain Cold Dredging Company, operations in Amador County, 231, 232 
Mud-pumping system, Yuba, description of, 59 
Mulligan Ratich. Placer County, 271 
Mullin and Company, operations in Tuolumne County, 313 

-Hampton Dredging Company, operations In Tuolumne County, 313, 315 
Munn property, Mariposa County, 261 
Murdock Ranch, San Joaquin County, 282 
Mutual mine. Placer County, 272 



.'UO 



N 



Xatoinas Company, jiy di-vcloiHiif nt by, Tl! ; dr.<lK.-s <i\viu-d l.y, ,',5 ; mining practices and 
eiiuipmont, 27,S-2.S0 : operations in Sacramento County, 1!TS- 280; photo 
showinK dredge of, 27!t 
iNeill, J. W., cited, U3 
Neizert iiropcity, Nevada County, 265 
Nevada County, placer mines in, 263-270 

Irrigation Distiict, 27" 
Neville property, SisUiyou Coimty, 298 
New Jersey mine, Placer County, 273 
Newark mine, Nevada County, 269 
Newcomb, R., cited, 13 

Nichols Estate Company, property in J'lacer County, 27 7 
Niece mine, Nevada County, 269 
No. 5 Channel, Calaveras County, 237, 238, 240 
Noble, <;. E., and Sons, mining operations in Madera County, 2G1 
Nordberg-Butler shovel, as used in Calaveias Central mine, 244-245 
North Bloomfield, Nevada County, 26:i ; Mining Company, 202, 260 

Columbia, Nevada County, 203 

Cow Creek, Shasta C<ninty, 284 

Fork hydraulic mine, Trinity County, 310-311 

San Juan, Nevada County, 263 
Northern Dredging Company, operations in Siskiyou County, 298 
Northwest Development ComiKiny, operations in Sacramento County, 281 

dragline excavator, 37 
Nozzles, water discharge through, 105 
Nugget Bar i>roperty. Trinity County, 305 
Nuland property, Calaveras County, 253 
Xuner property, Calaveras County, 253 
Nunes property, Siskiyou County, 298 



Occidental drift mine. Placer County, 272 

Ohio Plat, Tuolumne County, 315 

Okoro Mines, Inc., operations in Siskiyou County, 298 

Olson, K. S., operations in Shasta County, 284 

Omega mine, Nevada County, 265-260 

Ophir district, placer mining in, 272 

property, Yuba County, 315 
Ore buyers, laws regulating, 143 

Orick I'lacers, Inc., operations in Humboldt County, 258 
Orlomo Company, operations in El Dorado County, 256 
Oro mine, Placer County, 273 

Trinity Dredging Company, operations in Siskiyou County, 298 ; operations in 
Trinity County, 311 
Orono intervolcanic channel, 274 
Oroville area, as source of gold, 5'2 

Gold Dredging Company, operations in Butte County, 234 
Osterman property, San Joaquin County, 282 
Otter Creek, El Dorado County, 257 



P. & H. dragline excavator, 37 

I^acific Coast Aggi'egates, Inc., operations in Sacramento County, 282 

Gas & Electric Company, 270, 285, 289 

Placers Engineering Company, operations in Amador County, 232 
Page buckets, used on dragline excavators, 37 

Paleontologic criteria, determination of age of placers by, 184, 185 
Palmyra mine, Nevada County, 269 
I'an, description of gold-, 21-22 ; photo showing use of gold-, 14 

-American Engineering Company, 279 ; cited, 63, 65, 71, 73, 79 

-American Pulsator Jig, recent development, 69, 73, 74 
I'anob Gold Dredging Company, operations in Placer County, 275-276 
Pantle Bros., dry-land dredge used by, 49 ; operations in Placer County 
Paragon mine. Placer County, 273, 274, 276 
Pardee, J. T., cited, 169 ; quoted, 169 
Parker Ranch, Nevada County, 265 

Parks Bar Company, operations in Yuba County, 315 
Parmenter property, Trinity County, 305 
Patchen property, El Dorado County, 256 
Patman, C. G., cited, 139 
Patsy mine, Kern County, 260 
Pearch Creek, Humboldt County, 25 8 

mine, Humboldt County, 258-259 ; photo showing, 259 
Peele, Robert, cited, 9 7 
Peninsular Ranges, placer mining in, 157 
Penn property, Calaveras County, 253 
Penrose property, Mariposa County, 261 
Pension mine, Amador County, 232 



350 PLACER M1NIN<^ 1 OR OOM) IN CALIFORNIA | Bull. 13;") 

Perrin Ranch, Nevada Ciuiity, 208, 26U 
I'erschbaker mine, Butte Cuunty, 233 
I'erry Idlt-r, di scription of, 5!) ; photo showing, u8 
Petroleum industry, use of new exploration methods by, ir>4 
I'hillips property. Trinity County, 3oy , , . . , 

Phoenix river boat used for first dredi^ing attempt m ("alifornia, ;) 1 , :»2 
i'hysiographic criteria, determination of age of placers by, ISj 
geology, in study of gold-bearing streams, 207 
map of California, 158 
terms relating to streams, 194-195, 197 
Physiography, 153, 159 
Picacho iiasin placer mine. Imperial County, 2o'J 

lode mine. Imperial County, 259 
Piedmont Dredging Company, operations in liiitte County, 234 
I'ierano mine, Calaveras County, 230 
Pierce, C. C, property, Mariposa County, 2i;2 

J. T., Ranch, Aladera County, 2til 
Pillsbury, (J. B., cited, 145 

Pilot Dredging Company, operations in Nevada County, 2tir,, 270 
Pine Grove reservoir, Nevada County, 2ti5 
I'ingree Ranch, Nevada County, 2G.S, 2G9 
Piombo Bros. & Company, oi>erations in Butte County, 234 
IMoneer Dredging Company, operations in Shasta County, 2S4 
mine, old. Sierra County, 287 
Project mine, operations in Sierra County, 2S7 
Pipe, details for shipping, 101 ; photo showing installation for hydraulic mine, 100 
Pipelines, cost and method of laying, 102, 103; i<ressure boxes on, 102; type used in 

hydraulic mining, 100-105 
I'ipes, flow of water through, 103, 105; type used for flumes in British Columbia, 99; 

use of joints and valves on, 10_2 
Placer burials, as means of preservation, 171 

concentrators, operations in Kern County, 2(Hi 

County, dredging on Middle Fork American River, 25<; ; drift mining in, 157 ; placer 

mines in, 271-275 
Development Company, cited, 71 ; operations in Butte County, 234 
Exploration Company, operations in Butte County, 234-235 ; operations in Trinity 

County, 311, 313 
gold geologic processes in formation of, 173, 174; jigs used in recovery of, 63; 

marketing of, 142, 143 
jig, 55, 63, 66 

machines, small-scale, 31-33 

miners, number of small-scale during 1930's, 15 

mining, small-scale, as supplementary work, 13-14, 18 ; districts, legislation regard- 
ing, 336; methods, 11-146; small-scale methods, 13-33 
production, table showing ratio to lode production, 158 
Properties Company, operations in Stanislaus County, 304 
Realty Corporation, mining operations in Placer County, 272 
reserves, geologic classifications of, 152 
types, characteristics of the principal, 163, 165 
Placerita Canyon, Los Angeles County, 260 
I'laceritas Mining Company, operations in Amador County, 232 

Placers, age of, 183-186 ; characteristics of principal types, 163, 165-170 ; diagrammatic 
cross-sections showing transitional stages in development of, 162 ; forma- 
tion of, 65 ; geologic classification of, 161 ; geologic processes in modifica- 
tion of, 171, 173 ; preservation of, 171 ; sampling of large, 31 ; table showing 
cysfB of prospecting for, 224 
bajada, 161, 166 

beach, 161, 168-170; Pleistocene and Recent origin of, 205, 207 
depleted, 151 
desert, 197 
eluvial, 161, 163 
eolian, 161, 167 

glacial-stream, 161, 165 > 

stream, 161, 163 
Platinum metals, buyers of, 1930, 139, 140; in beach sands, economic Importance of, 
169 ; recovery In dragline dredging, 45 ; separation, 77, 78, 131-135, 137-140; 
significance in placer deposits, 219, 223; tools for separation of, 21 
Pleistocene, Red Bluff formation, 36 ; and Recent placers, 207 ; erosion, effect on Ter- 
tiary channels, 159; placers, 157. 165, 166, 201, 204, 205 
I'lumas Countv, placer mines in, 277 
Pole riffles, 123 

Polk Ranch, Madera County, 261 
Pontoons, for hull construction, 35, 59 
Potholes placer mine. Imperial County, 260 
Potter Ridge district, placer mining in, 261 

Poverty Hill Proi'erties, Sierra County, 286, 287, 289 ; photo of dredge under construc- 
tion, 286 
mine, Nevada County, 269 
I'owell mine, Nevada County. 269 
Power, for California dredges. 55 : for dragline dredges, 4 3 ; for single-bucket dredges, 62 

-winch for dragline dredge, photo showing. 40 
Prather. W. W., U. J. Alders and, mining operations in I'lacer County, 271 
Preservation of placers, descriptions of various methods of, 171 
Primitive gold recovery methods, photo showing, 14 



351 



I'rincess Tines property, Yuba County, SIT) ,„ , ^, . . 

rroduction of poid, lS4S-i;t14, talile showinR, lG-17 ; 1033-43. table showing, 35 
Prospecting, for l)iiriert rliannt'ls, Ifil 
Public domain, placer niininp on, 20-21 

lipsources Code, extract from, 33fi 
Puddling box, description of, 2S 
Pulsator jipr, 73, 74, 79 

Pumpelly, Pvaphael, cited, 171 ^ . , .. . . oo o- 

Pumps, in draprlinf dredge upi rat u.iis. 4..; in dntt mining, S.., Hi 

pravel. used in llrilish Coliimliia, lOS 

binvv diitv, in samplinp: machines, 31 
Putnam pnMi<rty, San Joaquin County, 2S2 



l^iiaker Hill, Nevada County, 2i;!t 
Quart7, Hill mine, photo showing, IH^ 

placers, operations in Calaveras County, 2r>3 

property, Calaveras Cf)unty, 2'>') 
Quaternary, placers of the, 151, ir)7, 1C6, ISfi 
Quicksilver, method of carrying, 130; price of, 12ft; use in recovering gold, 31, 42, 

f.;i, 70, 115, 120-13."), 130, 222. 223 
Quincy district, i)lacer mining in, 277 



R. & M. Mining Company, operations in Calaveras County, 253 ; operations In Yuba 

County, 313 
Raeburn, C, cited, lir, 
Rais Ranch. Shasta County, 2S4 

Ralford ^Mining Company, operations in Calaveras County, 253 
Rand Cold Dredging Associates, operation.s in Kern County, 260 
Raiulsl)urg district, placer mining in, 260, 2S2 
Ray Angle i)roi)erly, Butte County, 235 
Recalp Comijany, operations in Placer County, 272 
Recent and Pleistocene placers, 207 
Red p.luff formation, barren gravels in the, 30 

Dog Canvon, Nevada County, 200 
mine, Nevada County, 209, 270 

Hill mine, Trinity County, 307, 311 

Raven property. El Dorado County, 256 
Redding, dragline field southwest of, 3fi 

Creek, placer mining on, 311, 313 

mine, drawing showing Ruble elevator at, 108 ; phf)to showing Ruble elevator 
at, 110 
Reddings Creek I'lacer, Ltd., operations in Trinity Countv, 311-312 
Reed, Ralph D., cited, 171, 188 

property, Calaveras County, 253 
Rehberger property, Trinity County, 305 
Reiner mine, Calaveras Countv, 23G 

shaft, Calaveras County, 238 
Relief Hill mine, Nevada County, 2G6, 207-268 ; photo of, 268 
Reserves, placer, geolo.gic classification of, 152 
Re.servoirs, for hydraulic mining, 00, 100, 112 
Residual placers, geologic explanation of, 163 

Retort, amalgam, drawing showing, 138; used in gold extraction, 136, 137 
Rex mine, Trinity County, 313 
Richards, H. M., operation.s in Tuolumne County, 315 

R. H., cited, 77, 160 
Richter, William & Sons, ojierations in P.utte County, 235 ; operations in Nevada County, 
206 : operations in Sierra County, 289 ; photo showing dragline dredge 
of, 280 
Packard, T. A., cited, 161 
Ricketts, A. H., cited, 143, 323, 333 
Ries, H., diagrams by, 177 
Riffle claim. Sierra County, 287 

-tables, used with dragline dredge, 42 
Riffles, black-sand concentrates in, 77, 70 ; cleaning, in dragline recovery, 45 ; con- 
struction and use in hydraulic mining, 93, 115, 117 ; construction and use in 
rockers, 23: drawing showing block-type, 122; drawing showing dredge- 
and wooden block-type. 122; suitable for fine gravel, 127; suitable for 
shallow sluice streams, 125 : theor.\' of gold-saving by means of, 121 ; types 
suitable with undercurrent, 127 ; u.se in dip-box, 28, 29 ; use in sluicing, 29-30 

dredge-, 123; drawing showing cross-section, 43 

Hungarian, 45, 53, 115, 123 

iron, 118, 124, 125 ; -.screen, 125 

Jones, 73 

lumber, 123 

mercury trap, 53, 127 

miscellaneous, 127 

peeled-pole, 123 

rubber, 33, 60, 125 



:{.-,-J I'I.A(i:i< MININC I'OK (iOl.l) IN (AI.irOHNIA |BnlI. 13.") 

Riffles — Continued 

steel. 118. 124. 125 

stf.nc, 124 

slrt'iim-pi'bble, ?,0 

w.....I<-n-l.l..<-U. -.UK 12n-124 : diinviiiKs of. 122. 12.-!. 124 
Uiin Cam <:<>I<1 1 MfflniiiK Company, operations in Amador County, 232, 233 
Rio Dt-vtlopmoiil Company, oix-rations in Tuolumne County. 313 
River Pine Minin^r Company, ojurat ion.s in Amador County. 232, 256; operations in 

Kl Dorado County, 2.'ir. 
Rivers, diaj.'ram sliowinu di.wn-faiiltini; of lieil, 20.'. ; diagrams showing action of erosion 

and snciioii iddi.s in, 177 ; ma;;netic mithods of tracing channels, 227 
Rizzi Ranch, I'lae. i Connty. 271 
Roaring llivir, .Shasta <'omitv, 2S I : dredge, ruhlitr siil)stituted for iron in riffles. 42; 

Kr.djjlng Cmnpany, .Shasta County. 2r,0 
Robio lCst;ile, n)iniiig operations iii I'lacer County, 27" 

Ranoli, Calaveras County, 2.'.:! 
Robinson Ranch, I'laetr County, 272 
Rock Canyon Creek, 1*1 Dorado County, 2',:. 

Rocker, di-scription of, 22-2<;, 2'.i : drawing showing construitlon f)f knock-down, 24 : 
drawing showing iiarts used in consti net ion of, 2.". ; photo showing use of. 14 
Ropers Ranch. Placer County. 2 72 

Romanowitz. Charl.s .M., niirl.cl-Iinc drrduiufj, r,l-GO 
Kosa.sco propertv. Tuolumn'' Countv, 31:' 
Rose. I. K.. photr) by, 27.'. 

mine. Nevada Count.v, 2r.9 

propertv. .Siskivoti Countv. 2;tS ; Vulia Countv, .11.". 
Pvos.-villc Cold Dr.dging Company, operations in Placer County. 276 
Ross pro|i,iiv, Trinitv Countv. :'.(i."i 
Rossi property, .Sacramento County, 2S1 
Rolting.-r property, Hutte Cf)UiUy, 2:!.". 
Rf)Ugher-jig, (18, 69. 7.'5, 74 ; i)hoto showing 4-cell block. 74 ; concentrates, necessity and 

methods for testing. 67 : treatment of. 68, 69 
Roughness coefhcient ii. table showing values of, 96 
Roulard. V.. property, l-'resno County. 258 
Ruble elevator. <lrawing showing. lOS; photo showing, 110 
Ruby channel. 291 

mine, Si.rra County, 2S.S, 2.S9-292 ; cited, 81, 89; photo of, 2S8, 289; photo of gold 
nuggets frfim, 290 
Rnpley Ranch, Amador Count y, 2.T2 
P.ush Creek, Trinitv Countv, :!(I9 
Russell. Isra<-I C, cited, 1 .S'7 

Ranch, .Shasta Connty, 2S4 



Sacchi. Spellenborg, and Kubli, operations in Siskiyou County, 298 
Sacramento County, i)lacer mining in, 278-282 
mine. Placer County,- 273 
]{iver, recovery of gold from, 28.T 
-San Joaquin drainage, hydraulic mining on, 203 
Sailors Rar, Sacramento County, 2S1 

Salmon River. North Knrk, placer mining on, 275, 293, 298; South Fork, placer mining 
on. 294. 298 
district, jilacer mining in. 29.S 

<;old Dredging Company, operations in Siskiyou County, 298 
Mining Company, oiterations in Siskiyou County, 29:!, 29,s-:;o0 
Salyer mine, Trinity County, :{12 : photo of liyilraulic mining at, 1(",6 
Sampling, for hxdraulic mining, 220; machine, I'hoto of Bodinson, 30; placer deposits, 

31, 162, 219 
Sampson, R. J., cited, 167, 259, 260, 282 

San Andreas Cold Dredging Company, operations in Amador County, 232; operations 
tn Calaveras County. 253 
Hernardiiio County, placer mining in. 282 
Ruenaventura Mission. I.os Angeles County. 260 

Carlos <:old Dredging Comiiany. operations in Nevada County, 270 
Diego County, placer mining in, 157 
Domingo Creek, placer mining on, 251 
Kernamlo Mission, Los Angeles County, 260 
Krancisipiito Canyon, T.os Angeles County, 260 
(Jabrii'l Canyon, Los Angeh-s County, 260 
district, i)lacer mining in, 260 
Mission, Lr.s y\ngeles County. 260 
Cruco Companv, operations in Shasta County, 285; and C. 10. Cruwell, operations 

in San'.Ioa.piin County, 2S3 
.J.ia.piin Countv. pla<er miniug in. 2.S2-2S3 

Mining Conii>aiiy, operations in Merced County, 262 
River, placer mining on. 257 

Valley, drawing showing delta formation in. 198 
Juan Cold Company, operations in Nevada County, 266-267 ; water-rights of, 267 
Ridge, Nevada County, 266 
Sand-drag, photo showing, 76 
Sanguinetti Ridge, Tuolumne County, 313 



IXDEX 3r)3 

Santa Cruz, photo •showing placer mining of beach sands at, 168 

Felicia Canyon, Los Angeles County, 260 . „, „„ ^ , ^ j i 

Sawin, Herbert A., Becker-Hopkins single-bucket dredge, 61-62 ; Deep gravela dredged 
successfully, 317-322 ; and Romanowitz, C. M., Biicket-hne dredfftng, 51 

Scandia mine, Sisl<lyou County, 294-297 ; photo of dragline dredge at, 295 

Scavenger jig, 68, 69, 73, 74 

Scharr property. Trinity County, 305 

Schwab claim, Placer Colinty, 274 

Schwartz and Pedrazzini property, Butte County, 235 
property, Butte County, 235 

Scott paver, placer mining on, 298, 303, 311 

Scotts Flat, Nevada County, 266 ^ . , 

Screens, as feeder to undercurrent, 30 : for sizing black sands, 77 ; in Denver mechanical 
gold pan, 31 ; in dip-box, 27, 28 ; in long torn, 29 ; in rockers, 23, 26 ; standard 
size used on jigs, 66 
revolving, in bucket-line dredges, 53, 55 ; in dragline washing plant, 38, 41 ; in G-B 
portable placer machine, 33 ; in Monighan dragline excavator, 34 ; in 
sampling machines, 31 
wire, in Denver mechanical gold pan, 31 

Scrubber, in G-B portable placer machine, 33 ; -section, in Denver trommel-jig unit, 31 

Sears, Harry, cited, 236, 243 

Sedimentation, stream, 153, 154 

Seiad Valley, placer mining in, 300 

Setter property, El Dorado County, 256 

Shady Creek, Nevada County, 265 

Shaft-sinking, for testing placer deposits, 221 

Shafts, use in drift mining, 81, 82, 83 

Shanahan Bar, Trinity County, 313 

Shasta Countv, placer mining in, 283-285 
Dam, 283, 297 

Dredging Company, operations in Shasta County, 254; operations in Siskiyou 
County, 300 

Shepard, Francis P., cited, 171 

Shingle Springs, El Dorado County, 255 

Shirttail Canyon, Placer County, 272, 274 

Shuster. E. A., cited, 153 

Sierra County, placer mining in, 285-292 ; Ruby mine, 81 

Nevada, age of placers in, 183 ; block diagram showing effect of tilting on stream 
cutting, 199; diagram showing down-faulting of riverbed, 205; diagram 
showing epochs of Tertiary gravel deposition, 177 ; drainage system in, 
187; drift mining in foothills of, 81, 82; erosion in early Tertiary time, 
194; fossil plants in, 184: fossil vertebrate bones in, 185; geologic map 
showing topography of, 156 : geology of gold provinces in, 200-201, 204-206 ; 
geology of placer deposits in, 150, 152, 153, 159, 163, 173, 194, 204, 206; 
glacial placers in, 165, 166; gold in natural river sluices, 179; origin of 
gold in, 173 ; placer reserves in, 152 ; Pleistocene faulting in, 201, 204, 
205, 207 ; stream deposition in, 191 ; stream patterns in, 197, 205 ; stream 
piracy during Tertiary time, 195; Tertiary placers in, 157, 163, 171, 173, 
183, 200, 206, 207, 208 
Northern, ancient channels of, 155 
streams, glacial influence on, 205 

Silva property, Siskiyou Countv, 298 

Simpson, E. C, cited, 157 

Sinclair Ranch, Calaveras County, 253-254 

Single-bucket dredge, description of Becker-Hopkins, 61-62 

Siskiyou County, dragline dredge operations at Moccasin mine, 34, 35 ; dry-land dredge 
operation in, 50; eluvial placers in, 163; photos showing mines in, 164; 
placer mining: in, 293-303 

Six Bit Gulch. Tuolumne County. 313 

Slab Ranch, Calaveras County, 236, 237 ; shaft, 239 

Slate Creek, Yuba County, 315 

Slichter, diagram by, 198 

Sluice, photo showing, 126 

-box concentrates, separation of gold and platinum from, 131 

-boxe.s, 21 ; as rocker part. 23 ; at hydraulic mine, photo showing, 116 ; design and 
construction. 117; factors considered in determining width, 119; gold 
amalgamation in, 133 ; grades described, 120 ; handling of boulders in, 113, 
114; in long tom, 28, 29; influence of grade on capacity of, 120, 121; 
influence of grade on prold recovery from, 121 ; maintenance of, 118, 119- 
120; operating cost, 128; operating methods, 115, 117, 128; photo show- 
mg, 126 ; table giving size and capacity, 119 ; undercurrents installed with, 
127; use in hydraulic mining, 115, 117; use with Giant, 112 
short, 27 ; photo .^showing, 27 
-tailing, method of testing, 67 

Sluices, double purpose explained. 117; grade and size govern daily yardage, 112; 
improved operation in bucket-line dredging, 57 ; installation of jigs on, 
69-71 ; drawing showing jig arrangements, 70 ; use of auxiliary, in treating 
concentrates, 1 32 : use in hydraulic mining, 93, 113, 114 ; used with dragline 
dredge, 34, 38, 41, 42 ; used with dry-land dredge, 49, 50 ; use of mercury in. 
117, 130, 131 

Sluicing, description of, 29-30 ; in drift mining, 81 



:{r)4 I'LACr.K MININC von COM) IN CAMKORNIA |P.ull. liM 

Sm:ill II. .p,- niiiH", ria.-.T (•..imtv, •>::. 

-scuU: phircr mining' iiiftlxxls applitil tn l.laik >aii<l, ■ :• 
Sinartsvillc- ilistrirt. pla< <r miiiinp in, Ml.'. 
Smith, Ciiuit, property, Siskiyou ('minty. 21(4 

U. S., II. A. Smith and It. I. Smith, Dperatioiis in Trinity Ccunty. 312 

.1. 1'., cited, 1.S8 

I.. A., abstract from rei)ort by, 2tH-2il.'i 

mine, Nevada founty, 2r.9 

-Nnlti rman ("onipanv, operations in San .loarjuin t'ounty, 2s:; 
Smiths 1--I.it, i;i Dorail.i County, 2."..'. 

I'oint. ria.-er <'oiiiity, :j74 
.SnelliiiK dislrlet. placer niinintr in, 2f,2 

i:<il(l Dredcinj; Cc.nipiin.v. operations in .Merced County, 2<i2 
Solar! property, Ca la \ eras County, 2r,:', 

South Ynl.a .Miniiif,' and I ).\ elopnu-nt Company, operations in Nevada County, 2r,.-. 
Southern l'a( ilic Kailroad, 276 

SpilinK, in drift mininp:, .S5, St., ST : in loose j;rou?id, drawings showing, S4 
Spillways, on <1anis, <lit<'h«'S, and reservoirs, !•:• 
SpririK Creek, Nevada Cfninty, 21(7 
Spud Patch mine, San I'.ornardino Cr.unty, 2X2 
Spurr, J. K., cited, KIS : diagram l.y, )7ti 
Stackers, used with draf;line di-edne, 4:! 

Staj,':i" Mining Company, operations in Cala\eras County, 2'>.' 
Stanislaus County, placer niininR in, :'.04 

Kiver, placer mining f)n, :!04 
Starl)U<"k propt.Tty, 101 Dorado County, 2r)(i 
Starr mine, Ne\ailu County, 2119 

Steep Hollow, Nevada County, 203; Creek, Nevada County, 2(i!t 
Steffa. Don, cited, 2.-)l ; quoted, f>:i, 85, 86 
Stevenson, David, quoted, 188 

Stewart Cravel Mines, operations in Tlacer County, 270-277 
Stockton Ueservoir property, Calaveras County, 2.">:5 
Stoll, (',. !•:., property, I'lacer County, 275 
Stone riffles, 124 

Strai) Ravine, Placer County, 276 
Stratton property, Mariposa County, 2f.l 
Strauh Manufacturing Company, cited, 7;t 
Strawberry Valley district, placer inininp in, 315 

Stream deposition, 153, 17S-1S1, 1!tl-l!t4, 200; drawinj? showing several period.s of, 107; 
peoloRic explanation of. ]!tl-l!t4 ; of prold, 178-1. SI 

erosion. 171, 178, 1S7, 1SS, l!i7; ReoloKical explanati<.n of, 187, 188 

meandering. diaKi'am showinp oxbow loops in, l'.i2 

patterns. KeoloRic stiuly of, 181, 195, 107 

piracy, diagrams showiiifr stapes in, IftO 

placers. Keolopic exi.lanation of, 163, 105; Pleistocene fault origin, 204; Quater- 
nary oriRin, 151 ; Recent origin, 151 ; Tertiary, 208 

pollution laws, effect on bucket-line dredging, 51 

retention of gold, 178-181 

sedimentation, 153 

transportation, 188-191 ; of gold, 178-181 
Streams, life history of, 180-200; physiographic terms relating to, l!t4, 195, 197 : Sierra 
Nevada, glacial influence on, 205 ; subdividing or anastomosing, diagram 
showing, 192 
.Structural control, of streams, 195 

criteria, determination of age of placers by, 183, 184 
Stuarts Fork, l^Jast Fork of, placer mining on, 305 
Sullivan angle-compound cf)mpressors, use in <"alaveras Central mine, 241 

Creek, Tur>lunme County, 313 
Sultana mine, Calaveras County, 237 

Sumpter X'alley Dredging Company, i)liot<) supplied li.\ . 70 
Suimuir Dredging Comi)any, operations in I'.utle County. 2:;5 : operations in Vul>a 

County, 315 
Sunshine mine. Trinity County, 307 
Surveyors Mistake mine, Siskivou County, 30o 
Sutlers mill, di.scovery of gold at, 260 

Swanson Mining Corporation, operations in Trinity County. 312 ; photo supplied by, 100 
Sweetland, Nevada County, 263 
Sweetwater Creek, 101 Dorado County, 250 
Symons, Henry H., cited, 21 ; table of gold production, 10-17 



Table Mountain, 185, ISO, 19!i, 202, 203, 20 4 

Tadpole Creek, Shasta County, 283 

Tailings, jig recoveries from, 67, 73 ; method of testing, 67, 73 ; photo showing stacking 

with giant, 117; storage possibilities in hydraulic mining, 146; used for 

road-bullding, 53 
Tanner pro])erty, Calaveras County, 253 
Taylor mine. Nevada County, 269 

Tehama Dredging Company, o|)erations in Shasta <'ounty, 285 
Tennessee Manxman drift mine, Sieira County, 292 



M.V) 



T::r!:[a;^'d;a;!ranSl.';";:;l:;i'tio..s showing deposition. 177; placers in. 151. 152. 
175, ISO. 20G 

Oontral Hill cliannt;!. phot.. showinK, l;.l 

channel and its delta, early map showing. 1 .(. ,,;.,^,.v -.r ,i..v,.i 

channels, development of, 81. 82, 151, 152, ^^^ J •j•^J V,-,^ V-'l I'-'i 1 83 "^00 2 .- 
opment, 15!», Ifil; Sierra Nevada, 150, 1;>(, lb3, Id, l<.i, 183. 20(i. ^U, 

gravels, economic signilicance of, 157, 159 ,-o ir-,. 

physiography, relation to ancient-channel problem, li.3, 15 J 

sediments, as bedrock in dragline operation, 3C 

stream-piracy, 11(5 

stream-placers, reserves in, 207, 208 
Test pits, method and cost of running. 221 
Testing set. for jigs, photograph showing, 72 

tailing losses from dredges. 0(1, G7 
Texas mine. I'lacer County, 273 
Theller, J. H.. cited. 121 
Tliew-Lorain dragline excavator, 37 
Thoenen, J. K.. cited. 37 
Thomas, diagi'am by. 177 

property, Nevada County, 2G5 
Thompson, J., cited, I'JO 

J. F. Estate, property of. 27G 

W. C. mining operations in Calaveras County, 253-254 
Thorne property. San Joaquin County. 282 

Thurman and Wright, mining operations in Calaveras County, 253, 254 ; operations in 
Mariposa County, 261 ; operations in Merced County, 2G2 

C. H., cited, 254 

Cold Dredging Company, operations in Shasta County, 284-285 ; photo showing. 284 
Thursday No. 1 mine, Trinity County, 308 
Tickell, F. G., cited. 175 
Tiedemann mine. El Dorado County, 257 
Tightner formation, 291, 292 

'J'imber mats, for moving dragline excavators, 37 
Timbering, in drift mines, methods of, 85, 86, 87, 88, 91 ; in loose ground, drawings 

showing, 84 
Tin, jigs used in recovery of. 63 ; stream-, tools for separation of, 21 
Titan amalgamator, used with jigs, 7 4 
'Jolman. C. F.. cited, 16G 

Tomboy Gold Mines, operations in Calaveras County, 254 

Tonopah-Belmont Development Company, lease of Vallecito-Western mine to, 24 8 
Tout property. Trinity County, 313 
Trabucco property, Mariposa County, 261, 262 
Tractors, caterpillar, used with dragline dredges. 38 
Trailer, as mounting for sampling machines, 31 

Transportation, problems in mining bajada placers, 166 ; stream-. 178. 179, 181. 188-191 
Treble Clef mine, Amador County, 233 

Trebor Corixjration, operations in Mariposa County, 262 
Trimble property. Trinity County, 305 
Trinity and Klamath River fish and game district, legislation concerning, 334 

County, buried placers in, 171; bucket-line dredge operations in, 54, 55; placer 
mining in. 305-313 

Dredge, operations in Trinity County, 312-313 

River, photo showing hydraulicking of bench-gravel deposit, 166 ; placer mining on, 
258, 305, 309, 310, 313 ; bed, photo showing effect of early hydraulic mining 
in, 160 
Trommels, construction and use in dragline dredging, 41 ; for dragline dredge, photo 

showing, 40, 42 ; in Denver mechanical gold pan, 31 
Tucker, W. B., cited, 259, 260, 282 
Tungold mine, Kern County, 260 

Tungsten, jigs used in recovery of, 63 ; tools for separation of ore, 21 
Tuolumne County, photo showing andesite and breccia overlying volvanic-ash beds, 170 ; 
photo showing lava flow, 154 ; placer mining in, 313, 315 
Gold Dredging Corporation, operations in Stanislaus Countv. 304 
River, placer mining on. 304. 313 

Table Mountain, aerial mosaic photo and index sketch of, 202, 203 ; diagrammatic 
geologic cross-section of, 199 ; geology of, 185, 186 ; photo showing surface 
of, 204 
Turner property, Mariposa County, 261, 262 

Twin Bar Mining Corporation, operations in Fresno County, 258 
Two Channel mine, EI Dorado County, 257 
Tye property. Trinity County, 305 



Uncle Sam mine. Placer County, 273 

Undercurrent, description of, 30; definition of, 115, 131; method of gold recovery by. 

127, 128 
United States Bureau of Mines, geophysical studies by, 227 

Debris Commission, 273 

Geological Survey, investigation of valuable minerals in black sands by, 77 

Mint, instructions for shipping gold and silver to, 143 
Upper Narrows debris dam, Nevada County, 263, 266, 267 
Utica mine, Calaveras County, 237 



.'{.')() IM.ACDK MINI.VC lOK (iOM) IN CAl-IKOUN l\ IBull. l.M 



Viil UaiRli, Ciilax . I as Connfy, 2r.2 

Villdor DitilKiiiK I'oiiiimiiy, photo showing workiiiK-s of, I'lO 

\'iilU'<ito Mining ('iimpanv. Inc., operations in Culavt-ras County, 247, 248, 2r)l 

-\V'«sti-iii min«', drifting operations, 81, 83, 88, 247-2r>l, 254; geoloRy, 248; history. 
2r.l ; jotalion, l*4N; prii<lu( tion, 248, 250-251 ; washing plant of, 249-250 
Van Dyke, Modrdl, and W'arnt r, mining operations in l-^l Dorado County, 257 

Wagenen, T. K., <it.<l, 1 1 !• 
Vanciel, C. K.. operations in Calavt r.is County, 254 ; operations in Stanislaus County, 304 
Ventura mine, Kl Dorado County. 257 
Vesa Creek, Siskiyou County. ;tO() 
Victor mine, Calaxeras County, 2:!C 
Victory No. 2 mine. Kern County, 200 

Viking Dredging Company, operations in Trinity County, 311, 313 
Vincent, J., projierty, Sacramento t?ounty, 2S1 
Volcanic ash, as roof in drift mine, 88 
Volcano drift mine. Placer County, 27 7 

Mining Company, Dtd., operations in I'lacer County, 277 
Von der llellen. Wm., Dry-land dredge operations in Siskiyou County, 50 

and Welilter, operations in Siskiyou County, 300 

W 

Wallace Bros, mine, Trinity County, 311-312 

dredge, photo of, 230 
Walloupa mine, Nevada County, 2G9 
Waltz prop'rty, Mariposa County, 261, 2G2 
WaMilaiid, Dart, cited, 227 

War Production Hoard, limitations on gold mining, 34. Sit. 203. 268, 272, 289, 294, 315 
Washing i)lants, in dragline dredge operations, 38 ; in drift mining, 81 ; in dry-land 
dredge operations, 50 

all-steel, 39 
Washington mine, Nevada County, 269 ; Placer County, 273 

Water, duty in hydraulic mining, 112 ; flow through pipelines, 103, 104 ; heads required 
in hydraulic mining, 110, 112 

current, drawing showing effect of stream-bed irregularities on, 155 

rights, in hydraulic mining, 109, 146 ; on San Juan Gold Company holdings, Nevada 
County, 267 

supply, cost of, in dragline dredge operation, 43; determined by seasons, liiH; 
legislation protecting domestic, 335-336; imi)ortance in hvdraulic mining, 
93, 94, 146; use in small-scale placer mining, 19, 26 
Watkins, A. G., & Sons, operations in San Joaquin County, 283 
Watt, diagram by, 177 
Weaver Crock, Trinity County, 313 

Dredging Company, operations in Trinity County, 313 ; photo showing dragline 
dredge of, 312 
M'eaverville district, plac.r mining in, 305, 307, 313 
Webber, Benjamin N., cited, 161, 200; quoted, 166, 167 
Weber claim. Placer County, 27.4 
Welsh, Jack, Ranch, Stanislaus County, 304 
West mine, Nevada County, 269 
Western Gold, Inc., operations in Nevada County, 267-268 ; photo of Relief Hill mine, 268 

placer mine, Nevada County, 266-267 
What Cheer mine, Calaveras County, 254 
Wildcat Creek, Siskiyou County, 293, 303 

Wilfley tables, used in black-sand treatment, 77, 79, 80 ; used in dragline dredge clean- 
ups, 4 5 
William von der Hellen Mining Company, operations in Siskiyou County, 300 
Williams, G. S., cited, 93 

R., property. Mariposa County. 261 

Bar Dredging Company, operations in Yuba County, 315 
Wil.son, K. B., cited, 130 
Wiltsee, K. A., cited. 234 
Wiii.mler, N. D., cited, 96, 112 

Winches, used with dragline dredges, 37, 41 ; used with hydraulic dredges, 114 
Winchester claim, Placer County, 274 
Wolf Creek, Nevada County, 267 

vein, 292 
Wcilliull Dredging Corporation, oi)erations in Calaveras County, 254 
\\o,,(l strips, in riffles, 30 

Woodbury, W. K., f)perations in Trinity County, 313 
Wooden block riffles, 122, 123, 124 
Woods Creek, Tuolumne County, 315 

Works Progress Administration, report on small-scale placer mining, 13 
Wriglit, W. Q., cited, 181 
Wulff property. El Dorado County, 257 
Wyandotte Dredging Company, operations in Nevada County, 268-269, 270 

proi»erty, Butte County, 235 



nf)? 



Yager Ranch, Amador County, 233 

Yale and Allyn property, Calaveras County, 254 

You Ket, Nevada County, 269, 270 

district, placer mining in, 253, 269 
mines, Nevada County, 269-270 

Mining Company, operations in Nevada County, 270 
Young & Son Co., Ltd., operations in Calaveras County, 25 4 
Yreka, City of, property, Siskiyou County, 298 
Creek, Siskiyou County. 300 

(lold Dredging Company, operations in Siskiyou County, 300-303 ; photos of dredges, 
302 
Yuba bucket-line dredge, photo showing, 5 4 ; Trinity County operations, 55 

Consolidated Gold Fields, bucket-line dredges in California, 56; cited, 71; opera- 
tions in Butte County, 235 ; operations in Merced County, 262 ; operations 
in Siskiyou County, 303 ; operations in Stanislaus County, 304 ; operations 
in Trinity County, 305 ; operations in Yuba County, 315-322 ; photo of 
dredges, 314 
County, placer mining in, 315-322 ; single-bucket dredge being rebuilt in, 62 
jigs, on bucket-line dredges, 55 

Manufacturing Company, cited, 51, 61 ; descriptions of dredges built by, 303, 307 ; 
experiments with portable pontoons for hulls, 59 ; photos by, 230, 284, 286, 
314, 316, 320 
mud pumping svstems, description of, 59 
No. 20 dredge, photos of, 316, 320 

River, aerial photo of dredged strip on, 150 ; damming of, 263 
basin, placer mining in, 315 
Middle Pork, water-rights on, 267 
South Fork, use of water from, 265-266 



Zernitz, Emile, diagrams by, 198 ; quoted, 197 
Zig-zag riffles, in sluices, 30 



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